Ligand–Metal Complementarity in Rare-Earth and Actinide ChemistryClick to copy article linkArticle link copied!
- Conrad A. P. Goodwin*Conrad A. P. Goodwin*Email: [email protected]Department of Chemistry and Centre for Radiochemistry Research, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K.More by Conrad A. P. Goodwin
- Jordan F. Corbey*Jordan F. Corbey*Email: [email protected]Nuclear Material Processing Group, National Security Directorate, Pacific Northwest National Laboratory, Richland, Washington 99354, United StatesMore by Jordan F. Corbey
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The rare-earths are comprised of scandium, yttrium, and the lanthanides (atomic numbers 21, 39, and 57–71). (1) While these elements are essential to modern life, they were historically characterized as simple, perhaps dull, compared to the rich multielectron chemistry of d-block metals in catalysts and enzymes. These descriptions were quite fair and largely true at the time that these elements were being discovered and the first compounds containing them were being synthesized, although much progress has been made to overturn this view of the rare earths. Similarly, discussions about actinide chemistry are sometimes limited to research pertinent to the nuclear industry, which, while comprising technologies vital to modern society, does not celebrate the fascinating chemical space that much of the actinide series occupies. These historic characterizations of most of the rare-earth and actinide elements persist in some textbooks, and we acknowledge that it is a helpful place to start; however, altogether these series comprise 32 elements─27% of the 118 known by 2024─and we suggest it would be an unfortunate twist of physics if such a large proportion of the Periodic Table were genuinely dull. Indeed, as this Inorganic Chemistry Forum Issue “Ligand-Metal Complementarity in Rare-Earth and Actinide Chemistry” highlights, the chemistry─let alone the physics, that is, spectroscopy and magnetism─of these elements is rich and depends on ligands!
The “earth” part of “rare-earth elements” historically refers to ores that could be dissolved in mineral acids and the subsequent solid oxides obtained after processing. The “rare” part is often attributed to the rarity of gadolinite, the first ore from which individual rare-earth elements were isolated, which is found only in one location─Ytterby, Sweden. (2−4) Readers of Inorganic Chemistry will undoubtedly know that many rare-earth elements are not particularly rare, with the most abundant, cerium at 66.5 ppm in the Earth’s crust, being as common as copper at 60 ppm. (5) The least abundant nonradioactive member, thulium at 0.52 ppm, is roughly as prevalent as iodine at 0.45 ppm and more than 10 times as abundant as selenium at 0.05 ppm─the latter two of which are essential to life. (5) However, ores with economically viable concentrations of rare-earths are not common; they are unevenly dispersed around the world, and the separation of neighboring rare-earth elements from each other can be complex and tedious. By way of example, we mention the heroic work of James, who produced the first high-purity sample of thulium as various salts, a summary of which appeared in 1911. (6) Working in gallon-sized cast-iron vessels on multikilogram scales and relying upon fractional crystallization of bromate salts, James verified that “after about 15,000 operations the absorption spectrum underwent no change.” (6) Clearly, fractional crystallization of bromates works, but modern processes use ion-exchange resins that exploit the very small size differences between rare-earth cations to separate them more efficiently. (4)
The history of rare-earth element separation and the quest to obtain pure samples is littered with frustrating incremental advances, such as “pure” samples later being found to be mixtures by spectroscopic or chemical tests. Berzelius and Hisinger, along with Klaproth working independently, isolated cerium oxides or “ceria” from samples of gadolinite. (2) Mosander, a former student of Berzelius, found that upon further treatment, samples of ceria could be separated into at least three further fractions, one of which was dubbed “lanthan”, or lanthanum in English, derived from the Greek “λανθάνω” meaning hidden or to escape notice. The other two fractions were didymium, which was subsequently shown to be comprised of samarium, praseodymium, and neodymium─and also true ceria. (7) Thus, the lanthanide series derives its name from the hidden nature of its first member, lanthanum. Many of the fascinating developments in rare-earth and actinide chemistry over the past few decades have come about by challenging conventions and through advancements in ligand design to bring out the “hidden nature” of these elements.
In the modern era, samples of high-purity rare-earth (and to some extent early-actinide) materials are available in many research laboratories that wish to explore their properties in coordination complexes. Previous issues of Inorganic Chemistry have focused on ligand design strategies for f-element chelation (8) or trends of current exploration in lanthanide chemistry. (9) The impetus for this Forum Issue stems partly from our experiences of working either briefly or for an entire Ph.D. with one of the pioneers in f-element coordination chemistry, William J. Evans. Evans’ work in low-oxidation-state molecular chemistry, along with that of Michael Lappert, Geoffrey Cloke, and others, has redefined the limits of redox chemistry for all of the rare earths (save promethium due to its high radioactivity) and also thorium, and uranium through to plutonium; see refs (10−22) for just a small fraction of these works, with no implied preferences on our part. A defining feature of Evans’ career, which extends to the very first reactions with rare earths in his group, is the idea that if you put the right ligand on the right rare earth or actinide, exciting things will happen and that one should set assumptions, and the rulebook, aside when doing so. (23−25)
Throughout this Forum Issue there is an overarching theme of using specific ligands to tame the coordination environments of rare-earth (RE or Ln) and actinide (An) ions. Some of the research focuses on using different ligand systems to minimize oligomerization, or prevent the coordination of undesirable Lewis basic moieties, while others seek to characterize small or large multimetallic complexes that arise due to fine control of the ligand properties or solvent conditions. In the following sections, a brief overview of each paper is provided to tempt the reader into exploring some of the fascinating research being undertaken in this area.
While complexes of rare-earth cations are not known to engage in single-electron or multielectron catalytic reactions, they are all potent Lewis acids with similar coordination chemistry, which means that Lewis acid catalyst systems can be fine-tuned based on the metal size. Fieser and co-workers have examined the influence of axial Lewis-base donor properties in [RE(CH2SiMe3)3(THF)2] (RE = Y, Sm, Gd, Tm) precatalysts on the stereoselectivity and rate of isoprene polymerization. (26) Further variables, such as the rate and order of precursor addition and the stoichiometry of the catalyst activator, were all found to influence the reaction significantly, but under the right conditions, a living polymerization reaction was achievable. Zhu and Wang’s team further explored the Lewis acid chemistry of rare earths by demonstrating the insertion of a range of nitrile and isonitrile molecules into metal–alkyl bonds in [RE(L)(CH2SiMe3)(THF)2] (Ln = Y, Yb, Lu; L = {2,5-(2-C4H3N)CPh2)2(C4H2NMe)}) , forming unusual β-diketiminato, imidazolyl, and indolyl moieties. (27) For some of these, a dependence on both the reaction temperature and reaction stoichiometry is found, which shows that both kinetic and thermodynamic products can be accessed under appropriate conditions. (27) Continuing the theme of using rare-earth cations to assemble p-block atoms, Dehnen and co-workers shift our focus from carbon, to the heavy Group 13 and 15 members indium and bismuth. (28) While numerous examples of d-block ions encapsulated by Zintl phases are known, analogous rare-earth and actinide examples are rare. Treatment of the solid Zintl phase K10Ga3Bi6.65 with [In(Mes)3] (Mes = {C6H2-2,4,6-Me3}) and 2.2.2-cryptand in the presence of [La(C5Me4H)3] gives either the [La@In2Bi11]4– anion or the larger [{La@In2Bi11}2(μ-Bi)2]6–, where longer reaction times produce the latter, and hence, it is likely the thermodynamic product. In both, [K(2.2.2-cryptand)] cations provide charge balance. Bridging bismuth groups in the dimeric complex show interactions with one potassium cation each, somewhat “softening” the charge buildup on the indium sites, which have formal –2 charges, stabilizing this complex relative to the monomeric example. When the same reaction was explored without [La(C5Me4H)3], the researchers isolated a smaller cage in [Bi6(InMes)(InMes2)]3–, and also [{InMes3}2]2– from the same reaction, both as their [K(2.2.2-cryptand)] salts. This work demonstrates that the LaIII cation provides a significant stabilizing role in assembling larger cages. (28)
While the potent Lewis acidity and large coordination spheres of rare-earth cations are useful in building bigger bismuth cages, it makes the isolation of high-performance single-molecule magnets (SMMs) challenging because well-defined and specific coordination environments are required to maximize their properties. Several papers in this issue relate to the synthesis of different types of sandwich complexes; however, if you have ever wished to know “What is a sandwich complex?”, then an Editorial by Goodwin has this covered. (29) In their contribution, Chilton, Mills, and colleagues demonstrated that the sought-after SMM candidate [Dy(Cp*)2]+ (Cp* = {C5Me5}) cannot be isolated free of equatorial donor coordination, even when extremely weakly donating haloarenes are used, resulting in the first f-block bis-haloarene adducts [Dy(Cp*)2(PhX-κ-X)2][Al{OC(CF3)3}4] (X = F, Cl, Br). (30) Even when the size of the supporting ligands is increased, as in a second paper by Chilton and Mills that features [Dy(Cp*)(Cpttt)(XnC6H6–n)]+ (Cpttt = {C5H2-1,2,4-tBu3}), equatorial haloarene adducts could be isolated, although this class has better SMM characteristics than the previous due to the reduced equatorial donation. (31) Roesky and co-workers have explored the influence of arsolyl ligands, {η5-AsC4R4}, on the coordination environment and magnetic properties of several LnIII ions (Sm, Dy, and Er), finding that the nuclearity of [RE(η8-COT)(η5:μn-AsC4R4)]n (Ln = Sm, Dy, Er; n = 1, 2; COT = {C8H8}) complexes depends on the steric protection at the 2,5 positions of the {AsC4R4} ring with large SmIII ions, but with small DyIII and ErIII ions, monomeric complexes are obtained even with small R groups such as in {AsC4Me4}. The softer {AsC4R4} ligand gives magnetic properties at ErIII that are similar to those of the phosphorus analog, but slightly worse than those of the corresponding CpR (CpR = substituted Cp ligand) congeners. (32) Complexes of ErIII using the COT ligand, and 1,4-(trialkyl)silylated variants thereof, have been known for some time, and many have SMM properties. While regioisomers of silylated COT rings have been reported previously, methods for their purposeful isolation have remained elusive; therefore, the influence of multiple substitution patterns on the SMM properties of ErIII has not been systematically explored. In their work, Ding, Zhu, and Zheng’s team presented a unique twist on the area by exploring the differences between 1,3-, 1,4-, and also 1,5-substituted analogues of the {C8H6-(SiMe3)2} ligand on the SMM properties of ErIII complexes. (33) Rogachev, Shatruk, Petrukhina, and their team continued the COT sandwich complex theme but instead have focused on a benzannulated analogue, dibenzo[a,e]cyclooctatetraene (DBCOT), which forms charge-separated ion pairs, [RE(DBCOT)(THF)4][RE(DBCOT)2] (RE = Y, La, Gd, Tb, Dy, Er). (34) The SMM properties of the DyIII analogue were explored and showed a complicated relaxation pathway due to the presence of structurally dissimilar anionic and cationic DyIII fragments within the complex. (34)
Poor valence orbital overlap between trivalent rare-earth ions and ligand orbitals makes the isolation of multiply bonded species difficult because the linkages are highly polarized and very reactive. Thus, while alkylidenes and alkylidynes are well-represented with d-block ions, examples with rare-earth cations are much rarer or non-existent in the case of terminal unsupported variants. Nevertheless, in their contribution, Anwander’s group revisits and vastly expands the chemistry of [La(TptBu,Me)(μ3-CH2){μ-CH3(AlMe2)}2] (TptBu,Me = {HB(N2C3-2-Me-4-tBu)3}), previously reported by some of the same authors as the first lanthanide analogue of Tebbe’s reagent─[Ti(Cp)2{(μ-Cl)(μ-CH2)AlMe2]. (35) In this new work, routes to rare-earth methylidene complexes supported by TpR,R-type ligands were exhaustively explored, revealing a delicate balance between the ligand steric bulk, rare-earth ion radius, and ligand delivery route. For example, while [La(TptBu,Me)(μ3-CH2){μ-CH3(AlMe2)}2] can be isolated from the reaction of KTptBu,Me with [La(AlMe4)3], the reaction mixture contains additional products that have now been elucidated and result from the cleavage of N–B bonds in the TptBu,Me ligand and another that results from cyclometalation of pendant tBu groups on TptBu,Me along with a 1,2-borotropic shift of one of the pyrazolyl ligand arms. (35) An alternative route to methylidene complexes was explored via protonolysis between [RE(AlMe4)3] (RE = La, Nd) and HTptBu,Me, which produced dimeric [{RE(AlMe4-κ2Me)2}2(N2C3-2-tBu-4-Me)2] as the sole product. By switching to the smaller TpMe,Me ligand (TpMe,Me = {HB(N2C3-2,4-Me)3} and returning to salt-metathesis routes, the researchers were able to isolate methylaluminate complexes [RE(TpMe,Me)(AlMe4-κ2Me)(AlMe4-κMe)] with small Y and Lu, while methylidene complexes, [RE(TpMe,Me)(μ3-CH2){μ-CH3(AlMe2)}2], could be isolated with larger Nd and Sm. Their reactivity with ketones was also examined.
Contributions in the previous three sections have leveraged the Lewis acidity of rare-earth ions for chemical transformations or as part of designing molecular structures with desirable stereochemical properties to tune their electronic structures. Separate works by the groups of Knope (36) and also Vlaisavljevich and Daly (37) show another side of the Lewis acidity, where taming it requires judicious choice of reaction conditions and where seemingly minor ligand features can drive discrete product formation or distributions. The construction of high-nuclearity rare-earth clusters of defined composition has applications in catalysis, optical devices, and potentially fuel storage. However, a deeper understanding of the ligand and reaction conditions that produce specific clusters is challenging. For example, Knope and co-workers showed that using ethanol solvent in the reaction of Hacac (acac = {HC([C═O]CH3)2}) with Ce(NO3)3·(H2O)6 produces [Ce(acac)4], but changing the solvent to methanol leads to an oxo cluster with a {Ce6IVCe4IIIO8(OMe)4}16+ core; the subsequent addition of acetonitrile to this cluster further changes the core to {Ce10IVCe2IIIO12(OH)4}18+. This substantial change in the redox states of core cerium atoms from a simple change in the solvent conditions demonstrates the oxidative flexibility of these large oxo clusters. (36) Separate work by Vlaisavljevich’s and Daly’s groups showed that the solid-state speciation of lanthanide(III) (Nd, Sm, Tb, and Er) and uranium(III) phosphinodiboronates, {PR2(H3B)2} (R = iPr, Et, Me), has a large dependence on the identity of R groups at the phosphorus atom. Moreover, the authors showed that the degree of oligomerization in solution depends strongly on the identity of the R groups, which can be correlated to measurements of the B–P–B angles from the solid-state structures. (37) Allen and co-workers described their work on tris[2-(2-methoxyethoxy)ethyl]amine, an acyclic analogue to 2.2.2-cryptand (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane; or 2.2.2-crypt henceforth) designed to tame large and small rare-earth and actinide ions. With softer lanthanide(II) ions (Sm, Eu, and Yb) and an array of different counteranions, a huge variety of coordination modes and geometries can be realized, including monomers and dimers, neutral species, and separated ion pairs. (38) Alongside this, LaIII, CeIII, and UIII were successfully encapsulated in this new framework, and ultraviolet–visible-near-infrared absorption and luminescence spectroscopy of these, along with the X-ray photoelectron spectroscopy data of the LaIII and CeIII complexes, adds valuable insight into the coordination chemistry and photophysics of these ions across diverse environments. While LaIII cations in isolation are somewhat spectroscopically uninteresting, at least at visible wavelengths of light, due to the [Xe] closed-shell electron configuration, the solution chemistry of LaIII is often comparable to that of CeIII and UIII, due to similarities in their ionic radii, and so it acts as a useful diamagnetic surrogate for the exploration of new ligand frameworks for members at the start of the 4f and 5f rows. (39) In their contribution, La Pierre and co-workers explored a novel bulky phosphoramide ligand, {OP(NHtBu)(tBuNC2H4NtBu)}, with LaIII and showed that a variety of heteroleptic motifs can be isolated depending on the reaction stoichiometry. (40) For example, the reaction of 2 equivalents of K{OP(NHtBu)(tBuNC2H4NtBu)} with [LaI3(THF)4] in the presence of 4-dimethylaminopyridine (DMAP) afforded [La{OP(NHtBu)(tBuNC2H4NtBu)}2(I)(DMAP)], while the use of 3 equivalents of the K salt gave [La{OP(NHtBu)(tBuNC2H4NtBu)}3(THF)], where two of the ligands bind in a κO,N fashion and the third through the oxygen atom alone. The authors extended the work to show that complexes featuring a mixture of both anionic and neutral ligands could be isolated, as well as a benzyl derivative, [La{OP(NHtBu)(tBuNC2H4NtBu)}2(CH2Ph)(THF)]. The isolation of a heteroleptic fluoro-anilide complex, [La{OP(NHtBu)(tBuNC2H4NtBu)}3{N(H)C6H4-4-F}], was successful, but attempted deprotonation of the anilido N(H) group with benzylpotassium instead led to elimination of K{OP(NHtBu)(tBuNC2H4NtBu)}. (40) Extension of this flexible ligand set to other rare-earth cations is sure to open up interesting new chemical space.
The redox chemistry of rare-earth metals and their compounds is somewhat limited, although advances continue in this area in both high- and low-oxidation states. In the case of the elements samarium, europium, and ytterbium, their behavior often differs from the rest of the series, particularly so in the metallic state. (4) They are often able to act in oxidative addition chemistry to give products in the MII oxidation state under mild reaction conditions, much like the Group 2 elements. Junk, Jaroschik, and co-workers exploited this in their synthesis of ethylene-linked ansa-octaphenyllanthanocenes, [RE(C5Ph4CH2)2(THF)2] (RE = Sm, Eu, Yb), from 1,2,3,4-tetraphenylfulvene─itself reported via a novel route by these authors. (41) The EuII complex is luminescent and has been compared to related complexes [Eu(C5Ph4H)2(DME)] and [Eu(C5Ph5)2], revealing a complicated relationship between the degree of solvation, M···C5–centroid distance, and fluorescence emission maximum. (41) In contrast to the tendency of samarium, europium, and ytterbium to form divalent compounds, the team of Anderson, Klamm, Mason, and Tondreau report the oxidative dissolution of cerium and holmium metals in molten GaCl3, which affords trivalent [Ga][RE(GaCl4-κ2Cl)4] (RE = Ce, Ho) from the melt along with cocrystallized [Ga][GaCl4], (42) the former of which was purified by recrystallization from fluorobenzene to give [Ga(η6-FC6H5)2][RE(GaCl4-κ2Cl)4]. The oxidizing molten GaCl3 solvent conditions offer a rare route to soluble trivalent rare-earth complexes under mild conditions that do not require hydrocarbon solvents, except in a final purification step. Cerium is unique among rare earths in being able to access the tetravalent oxidation state across a wide range of ligand types and under both aerobic and anhydrous conditions. In their contribution, the groups of Bart and Schelter explored the redox chemistry of cerium with the noninnocent amidophenolate ligand “Clamp” (H6Clamp = {N(C6H4-2-NHC6H2-2-OH-3,5-tBu)3}), which is heptadentate and anchored with a basal amine group, and also the simple bidentate ligand, “ap” (H2ap = {HOC6H2-2-(NHDipp)-4,6-tBu}; Dipp = 2,6-di-iso-propylphenyl). (43) The groups found that CeIII complexes with both ligands exhibit metal- and ligand-centered redox events, which may help in the design of molecules that can engage in multielectron reactivity using metals, such as cerium, that are not conventionally able to do so. In their contribution, Walensky and co-workers explored the photophysics and electrochemistry of a mononuclear organometallic CeIII complex, [Ce(Cp*)2(ODipp)] (ODipp = OC6H3-2,6-iPr2), toward a better understanding of the ground- and excited-state electronic structures, and to determine the available redox chemistry. (44) As is typical of CeIII, they observed one intense dipole-allowed 4f → 5d excitation in the absorbance spectrum at 401 nm (ε = 3653 M–1 cm–1) along with a weaker shoulder at 347 nm (ε = 2000 M–1 cm–1), due relaxation to the two spin–orbit ground states (2F5/2 and 2F7/2). They found that this CeIII complex is readily oxidized with simple cuprous halides (CuCl, CuBr, CuI) to give structurally characterized mononuclear CeIV complexes [Ce(Cp*)2(ODipp)(X)] (X = Cl, Br, I). Transmetalation with AgF using either the bromo or iodo complexes gave [Ce(Cp*)2(ODipp)(F)], although the molecular structure was not determined. 1H NMR spectroscopy of these CeIV complexes reveals that as the halide series is descended, δ1H for the Cp* Me groups moves progressively downfield (i.e., Cl < Br < I), and electrochemistry shows that the CeIV/III couple becomes increasingly more anodic─that is, the complexes become more easily reduced with the heavier halides. (44) Curiously, the fluoride congener, [Ce(Cp*)2(ODipp)(F)], was found to be highly unstable, even in the solid state. The recalcitrant nature of rare-earth redox chemistry can instead be of benefit to certain areas of research. Multinuclear lanthanide complexes with radial-anion bridges have historically been record-setting SMMs, (45,46) and so a better understanding of the ligand (both bridging and ancillary at the metal) features that maximize desirable magnetic properties is patently important. In their contribution, Demir’s group used variable-temperature electron paramagnetic resonance spectroscopy combined with density functional theory (DFT) calculations to experimentally and computationally determine the ligand and metal spin density in mononuclear [Y{C(NiPr)2(N[SiMe3]2)}2(2,2′-bipy•)] (2,2′-bipy• = 2,2′-bipyridine radical anion) and dinuclear [Y{C(NiPr)2(N[SiMe3]2)}2]2(Bbim•)] (Bbim• = bis-benzimidizoyl radical anion) complexes. (47) The guanidinate ligand systems used in this study are highly customizable and represent tremendous scope for tuning the properties of future radical-bridged complexes using ligand design.
The actinides thorium, uranium, neptunium, and plutonium appear early in the 5f series and have isotopes with half-lives long enough to explore their chemistry in detail. They differ from rare-earth elements and transition metals in ways that sometimes give rise to divergent coordination chemistry and reactivity. The energetic proximity of valence 5f and 6d orbital sets means that highly covalent metal–element multiple bonding is possible under suitable conditions, most notably in the actinyl {AnO2}n+ linear dioxo species. (48) One powerful yet accessible technique for studying metal–element bonding in diamagnetic complexes is the combination of NMR spectroscopy alongside DFT calculations. This provides an experimental grounding to calculated results, and it has allowed Autschbach, Hayton, and co-workers to explore U–Caryl bonding in rare UVI organometallic species [Cat][UO2{C6H2-2,4,6-(CF3)3}3] (Cat = [Li(THF)3] or [Li(Et2O)3(THF)]). (49) They find appreciable covalent character in the U–Caryl bond and were able to excellently reproduce the experimental data, allowing them to describe trends in the 5f contribution to the bonding in these complexes and to compare this to other UVI organometallic complexes. (49) Continuing the theme of actinide-ligand covalency, the groups of Zi, Ding, and Walter reported a comparative tour de force case study between thorium(IV) and uranium(IV) imido complexes, [An(Cpttt)2(=NC6H4-4-Me)] (An = Th, U). (50) In this work, small structural differences, such as the uranium complex being slightly more sterically congested due to increased covalency, and hence tighter ligand binding, and the smaller size of UIV versus ThIV, are used to rationalize a substantial body of divergent reactivity. For example, the thorium complex reacts with internal alkynes to give [Th(Cpttt)2{N(C6H4-4-Me)C2R2-κN,C}] (R = Me, Ph), whereas the uranium analogue is unreactive. Conversely, because the redox chemistry of thorium is limited, the reaction with Ph2Se2 results in the Cpttt anion acting as a sacrificial reductant, producing a half-sandwich complex product, [Th(Cpttt)(SePh){μ-N(C6H4-4-Me)}]2, whereas the uranium analogue undergoes one-electron oxidation to give [U(Cpttt)2(═NC6H4-4-Me)(SePh)]. (50) Eisen and co-workers continued the theme of small-molecule reactivity with ThIV bent-metallocenes by exploring the reactivity of [Th(Cp*)2(Cl)2] with substituted cyclopropenyl imines, finding an unexpected temperature dependence. (51) The addition of {HN═C(CNR2)2} (R = iPr, Cy) to [Th(Cp*)2(Cl)2] at −20 °C affords simple Lewis-base adducts [Th(Cp*)2(Cl)2{HN═C(CNR2)2}] (R = iPr, Cy), where donation from the imine nitrogen atom to the metal increases aromatic stabilization in the cyclopropene ring. However, performing these reactions at room temperature causes the cyclopropene ring to be cleaved and gives [Th(Cp*)2(Cl)2{N≡C(CNR2)C(H)(NR2)}] (R = iPr, Cy), presumably via a 1,3-hydride shift. These studies were extended to the use of the methyl and mixed methyl/chloride complexes [Th(Cp*)2(Me)(R′)] (R′ = Cl, Me) under the same sets of contrasting conditions. Under kinetic control (i.e., at −20 °C), the methyl anion deprotonates these imines, but under the thermodynamic regime at room temperature, the cyclopropene rings are again cleaved. (51) In another show of how versatile the {M(Cp*)2}n+ framework is in rare-earth and actinide chemistry, Fortier and co-workers reported the isolation of a uranium cis-bis-phosphoranocarbene complex, [U(Cp*)2{C(H)PPh3}2], and explored its reactivity with alcohols. (52) This complex is competent in protonolysis reactions with, for example, HODipp, to give the monoaryloxide complex [U(Cp*)2{C(H)PPh3}(ODipp)], which itself can be reacted with stoichiometric or adventitious H2O to afford the mono-oxo complex [Ph3PCH3][UO(Cp*)2(ODipp)]. During the synthesis of [U(Cp*)2{C(H)PPh3}2] from [U(Cp*)2(Me)2], the authors identified an intermediate species, [U(Cp*)2{C(H)PPh3}(Me)], by 1H and 31P{1H} NMR spectroscopy and also found that thermolysis of the reaction mixture affords the metalated complex [U(Cp*)2{C(H)PPh2(C6H5-κC)}]. (52)
The single-electron and multielectron redox chemistry of uranium is well-known, as is the ability for UIII to engage in challenging reductions. (53,54) However, the formal UIV/III E1/2 for the archetypal uranium(III) silylamide complex [U(N″)3] (N″ = {N(SiMe3)2}) is only −1.4 V vs Fc+/0, which puts it comfortably outside the range of the reduction potential of processes such as the dearomatization of pyridine (ca. −2.9 V vs Fc+/0, though this will depend on the solvent used). While the UII complex [K(2.2.2-crypt)][U(N″)3] (E1/2 = −2.8 V vs Fc+/0 for UIII/II) is capable of this, it is a challenging compound to isolate. (55,56) Mazzanti and co-workers reported the isolation of a UIII cyclometalated complex, [K(2.2.2-cryptand)][U(N″)2{N(SiMe3)(SiMe2CH2-κN,C)], with an extremely negative UIV/III E1/2 of −2.6 V that is capable of reductively dimerizing pyridine. (57) This UIII complex was isolated in high yield from the room-temperature KC8 reduction of [U(N″)3] in the presence of 2.2.2-cryptand, liberating 1/2 equiv of H2 in the process. The ability to access UII-like reduction potentials from such a readily available precursor is sure to drive further work in this area. A vast array of exotic UIV element linkages are known, but in many instances, the oxidation of these to UV or UVI is not successful, so new and more strongly donating frameworks are attractive for this. In their work, Liddle reports the first use of a strongly donating and coordinatively flexible boryloxide ligand, {OB(NDippCH)2}, on an actinide. (58) By installation of the ligand on UIII using protonolysis with [U(N″)3] in toluene (i.e., free of coordinating solvents), the homoleptic [U{OB(NDippCH)2}3] complex was isolated, which features an η6-arene interaction between the uranium center and a single Dipp group. Salt metathesis between UCl4 and 3 equiv of K{OB(NDippCH)2} in THF gave pseudo-octahedral [U{OB(NDippCH)2}2(Cl)2(THF)2], where the two boryloxide groups are trans-disposed, along with unreacted K{OB(NDippCH)2}. When a two-step procedure was employed in which the previous reaction mixture was dried and then refluxed in toluene, the pseudo-trigonal-bipyramidal [U{OB(NDippCH)2}3(Cl)(THF)] complex could be isolated. The reaction of the UIII complex with adamantyl (Ad) azide afforded the uranium(IV) imido complex [U(NAd){OB(NDippCH)2}3], not only demonstrating the use of a new ligand class in actinide chemistry but also showing that it is capable of supporting uranium cations over at least three oxidation states.
The separation of actinide elements uranium, neptunium, and plutonium from lanthanide fission products in spent nuclear fuel is, while logistically demanding, somewhat readily achieved by their substantially different redox chemistries─accepting that neptunium is more complicated due to the propensity for the readily accessible{NpVO2}+ cation to disproportionate into NpIII and {NpVIO2}2+ and contaminate both the liquid and solid product streams. (48) Conversely, the transplutonium elements americium and curium predominantly exist as AnIII ions under aerobic conditions and have ionic radii similar to those of several LnIII ions that appear early in the series. (39) Therefore, separating these minor actinides from trivalent lanthanides is an ongoing challenge requiring the design of specialty ligand systems that exploit small differences in metal–ligand covalency to engender larger separation factors. (59−62) This experimentally demanding synthetic work sometimes shows that minute changes to the ligand frameworks can drive large differences in behavior. In their work, Wu and Shi’s team applied DFT calculations to rationalize the separation factors in two known phenanthroline-based extractants, alongside two novel frameworks, and found that the degree of nitrogen versus oxygen binding in these systems strongly influences their behavior and that softer ligands, which overall bind both AmIII and EuIII more weakly than harder ligands, offer better selectivity for AmIII over EuIII. (63) The divergence between the ligand binding in lanthanides versus actinides is often attributed to differences in the 4f vs 5f orbital contributions to bond formation. For actinides early in the series, thorium and uranium in particular, the availability of both 5f and 6d orbitals to accept donation from ligands often results in complex bond descriptions. Experimental methods to probe these properties exist, such as X-ray absorption spectroscopy, but luminescence spectroscopy combined with DFT calculations is a convenient laboratory-scale method to probe the nature of ligand-to-metal or metal-to-ligand charge-transfer events and hence begin to deconvolute the nature of the metal–ligand interaction. In their contribution, Milsmann’s and Matson’s groups explored the use of pyridine dipyrrolide ligands on both ThIV and UIV. (64) While both heteroleptic [Th(MesPDPPh)(Cl)2(THF)] (MesPDPPh = {NC6H3-2,6-(NC4H-3-Ph-5-Mes)2}) and homoleptic [Th(MesPDPPh)2] are highly luminescent, the UIV analogues are not, which is attributed to self-quenching due to ligand-to-metal charge transfer and transitions within the 5f manifold by analogy with d-block analogues with this ligand system. (64)
In conclusion, the collection of works in this Forum Issue “Ligand-Metal Complementarity in Rare-Earth and Actinide Chemistry” illuminates the expansive application space available to these elements that reside mainly near the bottom of the Periodic Table, at the nexus between catalysis, separation science, nuclear fuel research, molecular magnetism along with fundamental coordination/redox chemistries, and spectroscopy. Looking forward, we will not be surprised to see the pioneers in the field of rare-earth and actinide chemistry continue to push the limits of what is considered possible, especially into the heavier actinides, with the slow but steady addition of transuranium facility capabilities coming online in research institutions around the world.
Biographies
Jordan F. Corbey
Jordan F. Corbey earned her B.S. in Chemistry (2010) from Eastern Washington University and her Ph.D. in Chemistry (2015) from the University of California, Irvine, where she studied air-sensitive rare-earth and f-element coordination complexes under Prof. William J. Evans. Dr. Corbey is currently a staff scientist at Pacific Northwest National Laboratory in Richland, WA, where her research focuses on the synthesis and analysis of radioactive materials for national security missions.
Conrad A. P. Goodwin
Conrad A. P. Goodwin undertook his Ph.D. (2013–2017) at the University of Manchester, studying low-coordinate rare-earth and actinide coordination chemistry using sterically demanding bis-silylamide ligands under Prof. David P. Mills. He followed his graduate work with a brief postdoctoral position at the University of Manchester working on organometallic SMMs and then a J. Robert Oppenheimer Distinguished Postdoctoral Research Fellowship (2018–2021) at Los Alamos National Laboratory under Dr Andrew J. Gaunt. Dr. Goodwin is now a Royal Society University Research Fellow at the University of Manchester, where his group researches the physicochemical properties of rare-earth and actinide complexes with low and high oxidation states.
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- 14Arnold, P. L.; Cloke, F. G. N.; Hitchcock, P. B.; Nixon, J. F. The First Example of a Formal Scandium(I) Complex: Synthesis and Molecular Structure of a 22-Electron Scandium Triple Decker Incorporating the Novel 1,3,5-Triphosphabenzene Ring. J. Am. Chem. Soc. 1996, 118 (32), 7630– 7631, DOI: 10.1021/ja961253oGoogle Scholar14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XksVKksb8%253D&md5=e610715ffed9f82319c86fec807f1725The First Example of a Formal Scandium(I) Complex: Synthesis and Molecular Structure of a 22-Electron Scandium Triple Decker Incorporating the Novel 1,3,5-Triphosphabenzene RingArnold, Polly L.; Cloke, F. Geoffrey N.; Hitchcock, Peter B.; Nixon, John F.Journal of the American Chemical Society (1996), 118 (32), 7630-7631CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Cocondensation of Sc vapor with 2,2-dimethylpropylidynephosphine, [Me3CC≡P], affords the triple decker sandwich complex [(η5-tBu2C2P3)Sc(μ-η6:η6-tBu3C3P3)Sc(η5-tBu2C2P3)], which was structurally characterized by x-ray crystallog. The 1st example of a mol. Sc compd. in a formal oxidn. state of 1, this novel triple decker exhibits a remarkably low valence electron-no. of 22. It also displays the 1st structurally characterized example of a triphosphabenzene moiety ligand in a η6 fashion to a metal.
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- 16Blake, P. C.; Lappert, M. F.; Atwood, J. L.; Zhang, H. The synthesis and characterisation, including X-ray diffraction study, of [Th{η-C5H3(SiMe3)2}3]; the first thorium(III) crystal structure. J. Chem. Soc., Chem. Commun. 1986, 0 (15), 1148– 1149, DOI: 10.1039/C39860001148Google Scholar16https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2sXhtVant7s%253D&md5=b456c087ec20113a2280b1205da366f0The synthesis and characterization, including x-ray diffraction study, of [Th{η-C5H3(SiMe3)2}3]; the first thorium(III) crystal structureBlake, Paul C.; Lappert, Michael F.; Atwood, Jerry L.; Zhang, HongmingJournal of the Chemical Society, Chemical Communications (1986), (15), 1148-9CODEN: JCCCAT; ISSN:0022-4936.Redn. of ThL2Cl2 [L = η-1,3-bis(trimethylsilyl)cyclopentadienyl] with Na-K in PhMe gave the title complex I. The structure of I was detd. by x-ray crystallog. I is monomeric in the solid state with the 3 equiv. L groups distributed sym. about the quasi-9-coordinate Th.
- 17Blake, P. C.; Edelstein, N. M.; Hitchcock, P. B.; Kot, W. K.; Lappert, M. F.; Shalimoff, G. V.; Tian, S. Synthesis, properties and structures of the tris(cyclopentadienyl)thorium(III) complexes [Th{η5-C5H3(SiMe2R)2-1,3}3] (R = Me or tBu). J. Organomet. Chem. 2001, 636 (1–2), 124– 129, DOI: 10.1016/S0022-328X(01)00860-9Google ScholarThere is no corresponding record for this reference.
- 18Hitchcock, P. B.; Lappert, M. F.; Maron, L.; Protchenko, A. V. Lanthanum does form stable molecular compounds in the + 2 oxidation state. Angew. Chem., Int. Ed. 2008, 47 (8), 1488– 1491, DOI: 10.1002/anie.200704887Google Scholar18https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXisV2ltbk%253D&md5=f1905cc5b699ac01cf4300036f06ad1dLanthanum does form stable molecular compounds in the +2 oxidation stateHitchcock, Peter B.; Lappert, Michael F.; Maron, Laurent; Protchenko, Andrey V.Angewandte Chemie, International Edition (2008), 47 (8), 1488-1491CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Redn. of the LaIII tricyclopentadienide complex [LaCp"3] (Cp" = η5-1,3-(SiMe3)2C5H3) by K and [18]crown-6 or [2,2,2]cryptand produced thermally stable mononuclear cryst. lanthanate(II) salts. The La +2 oxidn. state in these complexes was confirmed both in soln. (EPR) and the solid state (EPR, SQUID, x-ray diffraction) and was supported by a computational study.
- 19Rice, N. T.; Popov, I. A.; Russo, D. R.; Bacsa, J.; Batista, E. R.; Yang, P.; Telser, J.; La Pierre, H. S. Design, Isolation, and Spectroscopic Analysis of a Tetravalent Terbium Complex. J. Am. Chem. Soc. 2019, 141 (33), 13222– 13233, DOI: 10.1021/jacs.9b06622Google Scholar19https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhsVGku7%252FI&md5=923fd66ea05faf580d6272d72dc06cc9Design, Isolation, and Spectroscopic Analysis of a Tetravalent Terbium ComplexRice, Natalie T.; Popov, Ivan A.; Russo, Dominic R.; Bacsa, John; Batista, Enrique R.; Yang, Ping; Telser, Joshua; La Pierre, Henry S.Journal of the American Chemical Society (2019), 141 (33), 13222-13233CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Synthetic strategies to yield mol. complexes of high-valent lanthanides, other than the ubiquitous Ce4+ ion, are exceptionally rare, and thorough, detailed characterization in these systems is limited by complex lifetime and reaction and isolation conditions. The synthesis of high-symmetry complexes in high purity with significant lifetimes in soln. and solid-state are essential for detg. the role of ligand-field splitting, multi-configurational behavior, and covalency in governing the reactivity and phys. properties of these potentially technol. transformative tetravalent ions. Authors report the synthesis and phys. characterization of an S4 sym., four-coordinate tetravalent terbium complex, [Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4] (where Et is Et and tBu is tert-butyl). The ligand field in this complex is weak and the metal-ligand bonds sufficiently covalent so that the tetravalent terbium ion is stable and accessible via a mild oxidant from the anionic, trivalent, terbium precursor, [(Et2O)K][Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4]. The significant stability of the tetravalent complex enables its thorough characterization. The step-wise development of the supporting ligand points to key ligand control elements for further extending the known tetravalent lanthanide ions in mol. complexes. Magnetic susceptibility, ESR spectroscopy, x-ray absorption near-edge spectroscopy (XAS), and d. functional theory studies indicate a 4f7 ground state for [Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4] with considerable zero-field splitting: demonstrating that magnetic, tetravalent lanthanide ions engage in covalent metal-ligand bonds. This result has significant implications for the use of tetravalent lanthanide ions in magnetic applications since the obsd. zero-field splitting is intermediate between that obsd. for the trivalent lanthanides and for the transition metals. The similarity of the multi-configurational behavior in the ground state of [Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4] (measured by Tb L3-edge XAS) to that obsd. in TbO2 implicates ligand control of multi-configurational behavior as a key component of the stability of the complex.
- 20Gompa, T. P.; Ramanathan, A.; Rice, N. T.; La Pierre, H. S. The chemical and physical properties of tetravalent lanthanides: Pr, Nd, Tb, and Dy. Dalton Trans. 2020, 49 (45), 15945– 15987, DOI: 10.1039/D0DT01400AGoogle Scholar20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXpvValsLw%253D&md5=7c9572fd5551a7e664a0ae23acd4c3f4The chemical and physical properties of tetravalent lanthanides: Pr, Nd, Tb, and DyGompa, Thaige P.; Ramanathan, Arun; Rice, Natalie T.; La Pierre, Henry S.Dalton Transactions (2020), 49 (45), 15945-15987CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)A review. The fundamental redox chem. and valence electronic structure of the lanthanides in mol. complexes and extended solids continues to be a fertile area of research. The contemporary understanding of the accessible oxidn. states of the lanthanide elements and the variability in their electronic structure is the result of several paradigm shifts. While the lanthanide elements have already found widespread use in tech. and consumer applications, the continued reevaluation of basic redox properties is a central chem. concern to establish a more complete description of periodic properties. This fundamental understanding of valence electronic structure as it is derived from oxidn. state and coordination environment is essential for the continued development of lanthanides in quantum information science and quantum materials research. This review presents the chem. and phys. properties of tetravalent lanthanide ions in extended solids and mols. with a focus on the elements apart from cerium: praseodymium, neodymium, terbium, and dysprosium.
- 21Palumbo, C. T.; Zivkovic, I.; Scopelliti, R.; Mazzanti, M. Molecular Complex of Tb in the + 4 Oxidation State. J. Am. Chem. Soc. 2019, 141 (25), 9827– 9831, DOI: 10.1021/jacs.9b05337Google Scholar21https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhtFaqs7bI&md5=174c3cd4d152142e3b1520c0b266679aMolecular Complex of Tb in the +4 Oxidation StatePalumbo, Chad T.; Zivkovic, Ivica; Scopelliti, Rosario; Mazzanti, MarinellaJournal of the American Chemical Society (2019), 141 (25), 9827-9831CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Lanthanides (Ln) usually occur in the +3, or more recently the +2, oxidn. states. The only example of an isolated mol. Ln4+ so far remains Ce4+. Here authors show that the +4 oxidn. state is also accessible in a mol. compd. of terbium as demonstrated by oxidn. of the tetrakis(siloxide)terbium(III) ate complex, [KTb(OSi(OtBu)3)4], 1-Tb, with the tris(4-bromophenyl)amminium oxidant, [N(C6H4Br)3][SbCl6], to afford the Tb4+ complex [Tb(OSi(OtBu)3)4], 2-Tb. The solid state structures of 1-Tb and 2-Tb were detd. by x-ray crystallog., and the presence of Tb4+ was unambiguously confirmed by ESR and magnetometry. Complex 2-Tb displays a similar voltammogram to the Ce4+ analog but with redox events that are about 1 V more pos.
- 22Willauer, A. R.; Palumbo, C. T.; Fadaei-Tirani, F.; Zivkovic, I.; Douair, I.; Maron, L.; Mazzanti, M. Accessing the + IV Oxidation State in Molecular Complexes of Praseodymium. J. Am. Chem. Soc. 2020, 142 (12), 5538– 5542, DOI: 10.1021/jacs.0c01204Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXktlOhs7g%253D&md5=f2222a8fbe3d3f246e223a2763e3fb52Accessing the +IV Oxidation State in Molecular Complexes of PraseodymiumWillauer, Aurelien R.; Palumbo, Chad T.; Fadaei-Tirani, Farzaneh; Zivkovic, Ivica; Douair, Iskander; Maron, Laurent; Mazzanti, MarinellaJournal of the American Chemical Society (2020), 142 (12), 5538-5542CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Out of the 14 lanthanide (Ln) ions, mol. complexes of Ln(IV) were known only for cerium and more recently terbium. Here we demonstrate that the +IV oxidn. state is also accessible for the large praseodymium (Pr) cation. The oxidn. of the tetrakis(triphenysiloxide) Pr(III) ate complex, [KPr(OSiPh3)4(THF)3], 1-PrPh, with [N(C6H4Br)3][SbCl6], affords the Pr(IV) complex [Pr(OSiPh3)4(MeCN)2], 2-PrPh, which is stable once isolated. The solid state structure, UV-visible spectroscopy, magnetometry, and cyclic voltammetry data along with the DFT computations of the 2-PrPh complex unambiguously confirm the presence of Pr(IV).
- 23Evans, W. J. Advances in f element reductive reactivity as a paradigm for expanding lanthanide and actinide science and technology. J. Alloys Compd. 2009, 488 (2), 493– 510, DOI: 10.1016/j.jallcom.2009.02.018Google ScholarThere is no corresponding record for this reference.
- 24Evans, W. J. Tutorial on the role of cyclopentadienyl ligands in the discovery of molecular complexes of the rare-earth and actinide metals in new oxidation states136†. Organometallics 2016, 35 (18), 3088– 3100, DOI: 10.1021/acs.organomet.6b00466Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFSjurnN&md5=afd9bc63ec9b7bc8cfb0707fde50d036Tutorial on the Role of Cyclopentadienyl Ligands in the Discovery of Molecular Complexes of the Rare-Earth and Actinide Metals in New Oxidation StatesEvans, William J.Organometallics (2016), 35 (18), 3088-3100CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)A review. This tutorial is based on the award address for the 2015 American Chem. Society Award in Organometallic Chem. sponsored by the Dow Chem. Company, Midland, Michigan. A fundamental aspect of any element is the range of oxidn. states accessible for useful chem. This tutorial describes the recent expansion of the no. of oxidn. states available to the rare earth and actinide metals in mol. complexes that has resulted through organometallic chem. involving the cyclopentadienyl ligand. These discoveries demonstrate that the cyclopentadienyl ligand, which has been a key component in the development of organometallic chem. since the seminal discovery of ferrocene in the 1950s, continues to contribute to the advancement of science. Background information on the rare earth and actinide elements is presented as well as the sequence of events that led to these unexpected developments in the oxidn. state chem. of these metals.
- 25Wedal, J. C.; Evans, W. J. A Rare-Earth Metal Retrospective to Stimulate All Fields. J. Am. Chem. Soc. 2021, 143 (44), 18354– 18367, DOI: 10.1021/jacs.1c08288Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXit1ygu73L&md5=4e94a23152b1b616add0c6f3d32fa65bA Rare-Earth Metal Retrospective to Stimulate All FieldsWedal, Justin C.; Evans, William J.Journal of the American Chemical Society (2021), 143 (44), 18354-18367CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A review. Formulating insightful questions and expts. is crucial to the advancement of science. The purpose of this Perspective is to encourage scientists in all areas of chem. to ask more "What if" questions: What if we tried this expt. What if we used these conditions. What if that idea is not correct. To stimulate this thinking, a retrospective anal. of a specific field, in this case rare-earth metal chem., is presented that describes the "What if" questions that could have and should have been asked earlier based on our current knowledge. The goal is to provide scientists with a historical perspective of discovery that exemplifies how previous views in chem. were often narrowed by predominant beliefs in principles that were incorrect. The same situation is likely to exist today, but we do not realize the limitations! Hopefully, this anal. can be used as a springboard for posing important "What if" questions that should be asked right now in every area of chem. research.
- 26Kosloski-Oh, S. C.; Knight, K. D.; Fieser, M. E. Enhanced Control of Isoprene Polymerization with Trialkyl Rare Earth Metal Complexes through Neutral Donor Support. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c03161Google ScholarThere is no corresponding record for this reference.
- 27Guo, D.; Hong, D.; Huang, Z.; Zhou, S.; Zhu, X.; Wang, S. Reactivity of Rare Earth Metal Alkyl Complexes with Nitriles or Isonitrile: Versatile Ways toward Multiply Functionalized β-Diketiminato, (Iso)indolyl, and Imidazolyl Chelating Rare Earth Metal Complexes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04079Google ScholarThere is no corresponding record for this reference.
- 28Pan, F.; Weinert, B.; Dehnen, S. Effect of La3+ on the Formation of Endohedral Zintl Clusters Featuring In/Bi Shells. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.4c00192Google ScholarThere is no corresponding record for this reference.
- 29Goodwin, C. A. P. What is a Sandwich Complex?. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.4c00243Google ScholarThere is no corresponding record for this reference.
- 30Corner, S. C.; Gransbury, G. K.; Vitorica-Yrezabal, I. J.; Whitehead, G. F. S.; Chilton, N. F.; Mills, D. P. Synthesis and Magnetic Properties of Bis-Halobenzene Decamethyldysprosocenium Cations. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04106Google ScholarThere is no corresponding record for this reference.
- 31Corner, S. C.; Gransbury, G. K.; Vitorica-Yrezabal, I. J.; Whitehead, G. F. S.; Chilton, N. F.; Mills, D. P. Halobenzene Adducts of a Dysprosocenium Single-Molecule Magnet. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04105Google ScholarThere is no corresponding record for this reference.
- 32Schwarz, N.; Krätschmer, F.; Suryadevara, N.; Schlittenhardt, S.; Ruben, M.; Roesky, P. W. Synthesis, Structural Characterization, and Magnetic Properties of Lanthanide Arsolyl Sandwich Complexes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c03374Google ScholarThere is no corresponding record for this reference.
- 33Chen, Q.-W.; Ding, Y.-S.; Zhu, X.-F.; Wang, B.-W.; Zheng, Z. Substituent Positioning Effects on the Magnetic Properties of Sandwich-Type Erbium(III) Complexes with Bis(trimethylsilyl)-Substituted Cyclooctatetraenyl Ligands. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c03369Google ScholarThere is no corresponding record for this reference.
- 34Zhu, Y.; Mahoney, J.; Babson, A. J.; Zhou, Z.; Wei, Z.; Gakiya-Teruya, M.; McNeely, J.; Rogachev, A. Y.; Shatruk, M.; Petrukhina, M. A. Homoleptic Rare-Earth-Metal Sandwiches with Dibenzo[a,e]cyclooctatetraene Dianions. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04249Google ScholarThere is no corresponding record for this reference.
- 35Schädle, D.; Litlabø, R.; Meermann-Zimmermann, M.; Thim-Spöring, R.; Schädle, C.; Maichle-Mössmer, C.; Törnroos, K. W.; Anwander, R. Rare-Earth-Metal Methyl and Methylidene Complexes Stabilized by TpR,R′-Scorpionato Ligands─Size Matters. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04422Google ScholarThere is no corresponding record for this reference.
- 36Blanes-Díaz, A.; Shohel, M.; Rice, N. T.; Piedmonte, I.; McDonald, M. A.; Jorabchi, K.; Kozimor, S. A.; Bertke, J. A.; Nyman, M.; Knope, K. E. Synthesis and Characterization of Cerium-Oxo Clusters Capped by Acetylacetonate. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02141Google ScholarThere is no corresponding record for this reference.
- 37Zgrabik, J. C.; Bhowmick, R.; Eckstrom, F. D.; Harrison, A. R.; Fetrow, T. V.; Blake, A. V.; Vlaisavljevich, B.; Daly, S. R. The Influence of Phosphorus Substituents on the Structures and Solution Speciation of Trivalent Uranium and Lanthanide Phosphinodiboranates. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02773Google ScholarThere is no corresponding record for this reference.
- 38Bokouende, S. S.; Kulasekara, D. N.; Worku, S. A.; Ward, C. L.; Kajjam, A. B.; Lutter, J. C.; Allen, M. J. Expanding the Coordination of f-Block Metals with Tris[2-(2-methoxyethoxy)ethyl]amine: From Molecular Complexes to Cage-like Structures. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02752Google ScholarThere is no corresponding record for this reference.
- 39Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr. A 1976, 32 (5), 751– 767, DOI: 10.1107/S0567739476001551Google ScholarThere is no corresponding record for this reference.
- 40Boggiano, A. C.; Bernbeck, M. G.; Jiang, N.; La Pierre, H. S. Coordination Modes and Binding Patterns in Lanthanum Phosphoramide Complexes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04521Google ScholarThere is no corresponding record for this reference.
- 41Shephard, A. C. G.; Delon, A.; Chevreux, S.; Martinez, A.; Guo, Z.; Deacon, G. B.; Lemercier, G.; McClenaghan, N.; Jonusauskas, G.; Junk, P. C.; Jaroschik, F. Divalent ansa-Octaphenyllanthanocenes: Synthesis, Structures, and EuII Luminescence. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c01062Google ScholarThere is no corresponding record for this reference.
- 42Fetrow, T. V.; Cashman, B. K.; Carpenter, S. H.; Janicke, M. T.; Anderson, N. H.; Klamm, B. E.; Mason, H. E.; Tondreau, A. M. Oxidative Dissolution of Lanthanide Metals Ce and Ho in Molten GaCl3. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02774Google ScholarThere is no corresponding record for this reference.
- 43Uruburo, C.; Rupasinghe, D. M. R. Y. P.; Gupta, H.; Knieser, R. M.; Lopez, L. M.; Furigay, M. H.; Higgins, R. F.; Pandey, P.; Baxter, M. R.; Carroll, P. J.; Zeller, M.; Bart, S. C.; Schelter, E. J. Metal–Ligand Redox Cooperativity in Cerium Amine-/Amido-Phenolate-Type Complexes. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02411Google ScholarThere is no corresponding record for this reference.
- 44Gremillion, A. J.; Ross, J.; Yu, X.; Ishtaweera, P.; Anwander, R.; Autschbach, J.; Baker, G. A.; Kelley, S. P.; Walensky, J. R. Facile Oxidation of Ce(III) to Ce(IV) Using Cu(I) Salts. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04337Google ScholarThere is no corresponding record for this reference.
- 45Rinehart, J. D.; Fang, M.; Evans, W. J.; Long, J. R. A N23- radical-bridged terbium complex exhibiting magnetic hysteresis at 14 K. J. Am. Chem. Soc. 2011, 133 (36), 14236– 14239, DOI: 10.1021/ja206286hGoogle Scholar45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVGjtbjF&md5=f239373765668d7ca490e1fa63b55f32A N23- Radical-Bridged Terbium Complex Exhibiting Magnetic Hysteresis at 14 KRinehart, Jeffrey D.; Fang, Ming; Evans, William J.; Long, Jeffrey R.Journal of the American Chemical Society (2011), 133 (36), 14236-14239CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The synthesis, crystal structures and magnetic properties of three new N23- radical-bridged dilanthanide complexes, [K(18-crown-6)(THF)2]{[(Me3Si)2N]2(THF)Ln}2(μ-η2:η2-N2)·nTHF (Ln = Tb, Ho, Er; n = 0, 2, 2, resp.), are reported. All three display signatures of single-mol.-magnet behavior, with the terbium congener exhibiting magnetic hysteresis at 14 K and a 100 s blocking temp. of 13.9 K. Synergizing the strong magnetic anisotropy of terbium(III) with the effective exchange-coupling ability of the N23- radical can create the hardest mol. magnet discovered to date. Through comparisons with nonradical-bridged a.c. magnetic susceptibility measurements, the magnetic exchange coupling hinders zero-field fast relaxation pathways, forcing thermally activated relaxation behavior over a much broader temp. range.
- 46Rinehart, J. D.; Fang, M.; Evans, W. J.; Long, J. R. Strong exchange and magnetic blocking in N23– radical-bridged lanthanide complexes. Nat. Chem. 2011, 3 (7), 538– 542, DOI: 10.1038/nchem.1063Google ScholarThere is no corresponding record for this reference.
- 47Delano, F. I. V.; Deshapriya, S.; Demir, S. Guanidinate Yttrium Complexes Containing Bipyridyl and Bis(benzimidazolyl) Radicals. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.4c00006Google ScholarThere is no corresponding record for this reference.
- 48Morss, L. R.; Edelstein, N. M.; Fuger, J. The Chemistry of the Actinide and Transactinide Elements; Springer: Dordrecht, The Netherlands, 2011. DOI: 10.1007/978-94-007-0211-0 .Google ScholarThere is no corresponding record for this reference.
- 49Ordoñez, O.; Yu, X.; Wu, G.; Autschbach, J.; Hayton, T. W. Quantifying Actinide–Carbon Bond Covalency in a Uranyl–Aryl Complex Utilizing Solution 13C NMR Spectroscopy. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02440Google ScholarThere is no corresponding record for this reference.
- 50Li, T.; Heng, Y.; Wang, D.; Hou, G.; Zi, G.; Ding, W.; Walter, M. D. Uranium versus Thorium: A Case Study on a Base-Free Terminal Uranium Imido Metallocene. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c03356Google ScholarThere is no corresponding record for this reference.
- 51Deka, H.; Fridman, N.; Eisen, M. S. Temperature Dependence of the Ring Opening of Cyclopropene Imines on Thorium Metallocenes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04213Google ScholarThere is no corresponding record for this reference.
- 52MacGregor, F.; Tarula-Marin, J. L.; Metta-Magaña, A.; Fortier, S. A Metallocene Bis(phosphoranocarbene) of Uranium and a Probe of Its Reactivity with Alcohols. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04565Google ScholarThere is no corresponding record for this reference.
- 53Arnold, P. L.; Mansell, S. M.; Maron, L.; McKay, D. Spontaneous reduction and C-H borylation of arenes mediated by uranium(III) disproportionation. Nat. Chem. 2012, 4 (8), 668– 674, DOI: 10.1038/nchem.1392Google Scholar53https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtVehtr%252FN&md5=d8e8ebaa426599aad1c67fc930ea7a8aSpontaneous reduction and C-H borylation of arenes mediated by uranium(III) disproportionationArnold, Polly L.; Mansell, Stephen M.; Maron, Laurent; McKay, DavidNature Chemistry (2012), 4 (8), 668-674CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Transition-metal-arene complexes such as bis(benzene)chromium, Cr(η6-C6H6)2, are historically important to d-orbital bonding theory and have modern importance in org. synthesis, catalysis and org. spintronics. In studies of f-block chem., however, arenes are invariably used as solvents rather than ligands. Here, simple U complexes, UX3 (X = aryloxide, amide), spontaneously disproportionate, transferring an electron and X-ligand, allowing the resulting UX2 to bind and reduce arenes, forming inverse sandwich mols. [X2U(μ-η6:η6-arene)UX2] and a UX4 byproduct. Calcns. and kinetic studies suggest a cooperative small-mol. activation' mechanism involving spontaneous arene redn. as an X-ligand is transferred. These mild reaction conditions allow functionalized arenes such as arylsilanes to be incorporated. The bulky UX3 are also inert to reagents such as boranes that would react with the traditional harsh reaction conditions, allowing the development of a new in situ arene C-H bond functionalization methodol. converting C-H to C-B bonds.
- 54Liddle, S. T. The Renaissance of Non-Aqueous Uranium Chemistry. Angew. Chem., Int. Ed. 2015, 54 (30), 8604– 8641, DOI: 10.1002/anie.201412168Google Scholar54https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtVSju7rL&md5=831c0bb3d55c28b6d7809bb1de201a04The Renaissance of Non-Aqueous Uranium ChemistryLiddle, Stephen T.Angewandte Chemie, International Edition (2015), 54 (30), 8604-8641CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. Prior to the year 2000, nonaq. uranium chem. mainly involved metallocene and classical alkyl, amide, or alkoxide compds. as well as established carbene, imido, and oxo derivs. Since then, there was a resurgence of the area, and dramatic developments of supporting ligands and multiply bonded ligand types, small-mol. activation, and magnetism are reported. This Review (1) introduces the reader to some of the specialist theories of the area, (2) covers all-important starting materials, (3) surveys contemporary ligand classes installed at U, including alkyl, aryl, arene, carbene, amide, imide, nitride, alkoxide, aryloxide, and oxo compds., (4) describes advances in the area of single-mol. magnetism, and (5) summarizes the coordination and activation of small mols., including CO, CO2, nitric oxide, dinitrogen, white phosphorus, and alkanes.
- 55Ryan, A. J.; Angadol, M. A.; Ziller, J. W.; Evans, W. J. Isolation of U(II) compounds using strong donor ligands, C5Me4H and N(SiMe3)2, including a three-coordinate U(II) complex. Chem. Commun. 2019, 55 (16), 2325– 2327, DOI: 10.1039/C8CC08767AGoogle Scholar55https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXkvVSltQ%253D%253D&md5=d345cf3009e9d25f1ad605d50d2009f9Isolation of U(II) compounds using strong donor ligands, C5Me4H and N(SiMe3)2, including a three-coordinate U(II) complexRyan, Austin J.; Angadol, Mary A.; Ziller, Joseph W.; Evans, William J.Chemical Communications (Cambridge, United Kingdom) (2019), 55 (16), 2325-2327CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)New examples of uranium in the formal +2 oxidn. state have been isolated by redn. of Cptet3U (Cptet = C5Me4H) and U(NR2)3 (R = SiMe3) in the presence of 2.2.2-cryptand (crypt) to produce [K(crypt)][Cptet3U] and [K(crypt)][U(NR2)3], resp. Both complexes have properties consistent with 5f36d1 electron configurations and demonstrate that the U(II) ion can be isolated with electron donating ligands.
- 56Modder, D. K.; Palumbo, C. T.; Douair, I.; Fadaei-Tirani, F.; Maron, L.; Mazzanti, M. Delivery of a Masked Uranium(II) by an Oxide-Bridged Diuranium(III) Complex. Angew. Chem., Int. Ed. 2021, 60 (7), 3737– 3744, DOI: 10.1002/anie.202013473Google Scholar56https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXis1ShurrK&md5=993958f6e2d6d3d6f4014fe93dc20da1Delivery of a Masked Uranium(II) by an Oxide-Bridged Diuranium(III) ComplexModder, Dieuwertje K.; Palumbo, Chad T.; Douair, Iskander; Fadaei-Tirani, Farzaneh; Maron, Laurent; Mazzanti, MarinellaAngewandte Chemie, International Edition (2021), 60 (7), 3737-3744CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Oxide is an attractive linker for building polymetallic complexes that provide mol. models for metal oxide activity, but studies of these systems are limited to metals in high oxidn. states. Herein, authors synthesized and characterized the mol. and electronic structure of diuranium bridged UIII/UIV and UIII/UIII complexes. Reactivity studies of these complexes revealed that the U-O bond is easily broken upon addn. of N-heterocycles resulting in the delivery of a formal equiv. of UIII and UII, resp., along with the uranium(IV) terminal-oxo coproduct. In particular, the UIII/UIII oxide complex effects the reductive coupling of pyridine and two-electron redn. of 4,4'-bipyridine affording unique examples of diuranium(III) complexes bridged by N-heterocyclic redox-active ligands. These results provide insight into the chem. of low oxidn. state metal oxides and demonstrate the use of oxo-bridged UIII/UIII complexes as a strategy to explore UII reactivity.
- 57Modder, D. K.; Scopelliti, R.; Mazzanti, M. Accessing a Highly Reducing Uranium(III) Complex through Cyclometalation. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c03668Google ScholarThere is no corresponding record for this reference.
- 58Dan, X.; Du, J.; Zhang, S.; Seed, J. A.; Perfetti, M.; Tuna, F.; Wooles, A. J.; Liddle, S. T. Arene-, Chlorido-, and Imido-Uranium Bis- and Tris(boryloxide) Complexes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04275Google ScholarThere is no corresponding record for this reference.
- 59Panak, P. J.; Geist, A. Complexation and Extraction of Trivalent Actinides and Lanthanides by Triazinylpyridine N-Donor Ligands. Chem. Rev. 2013, 113 (2), 1199– 1236, DOI: 10.1021/cr3003399Google Scholar59https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhslSqtrw%253D&md5=96ab70f9b40c9a2f1e4a9a5782d83c4dComplexation and Extraction of Trivalent Actinides and Lanthanides by Triazinylpyridine N-Donor LigandsPanak, Petra J.; Geist, AndreasChemical Reviews (Washington, DC, United States) (2013), 113 (2), 1199-1236CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. The following topics are discussed:Lipophilic Bistriazinylpyridines (BTP); Lipophilic Bistriazinyl Bipyridines (BTBP); Water-Sol. BTP and BTBP; Complexation of An(III) and Ln(III) with BTP and BTBP and structure of the complexes; extn. of the complexes; studies using UV/Vis Spectrophotometry, ESI-MS, NMR methods; thermodn. data and description.
- 60Gelis, A. V.; Lumetta, G. J. Actinide Lanthanide Separation Process─ALSEP. Ind. Eng. Chem. Res. 2014, 53 (4), 1624– 1631, DOI: 10.1021/ie403569eGoogle Scholar60https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXmsVShsg%253D%253D&md5=5a910eaa3b20a8a625b814895dcdbc83Actinide Lanthanide Separation Process-ALSEPGelis, Artem V.; Lumetta, Gregg J.Industrial & Engineering Chemistry Research (2014), 53 (4), 1624-1631CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)Sepn. of the minor actinides (Am, Cm) from the lanthanides at an industrial scale remains a significant tech. challenge for closing the nuclear fuel cycle. To increase the safety of used nuclear fuel (UNF) reprocessing, as well as reduce assocd. costs, a novel solvent extn. process has been developed. The process allows for partitioning minor actinides, lanthanides, and fission products following uranium/plutonium/neptunium removal, minimizing the no. of sepn. steps, flowsheets, chem. consumption, and waste. This new process, actinide lanthanide sepn. (ALSEP), uses an org. solvent consisting of a neutral diglycolamide extractant, either N,N,N',N'-tetra-(2-ethylhexyl)-diglycolamide (T2EHDGA) or N,N,N',N'-tetraoctyldiglycolamide (TODGA), and an acidic extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH-[EHP]), dissolved in an aliph. diluent (e.g., n-dodecane). The An/Ln coextn. is conducted from moderate-to-strong nitric acid, while the selective stripping of the minor actinides from the lanthanides is carried out using a polyaminocarboxylic acid/citrate buffered soln. at pH anywhere between 3 and 4.5. The extn. and sepn. of the actinides from the fission products is very effective in a wide range of HNO3 concns., and the min. sepn. factors for lanthanide/Am exceed 30 for Nd/Am, reaching >60 for Eu/Am under some conditions. The exptl. results presented here demonstrate the great potential for a combined system, consisting of a neutral extractant such as T2EHDGA or TODGA, and an acidic extractant such as HEH-[EHP], for sepg. the minor actinides from the lanthanides.
- 61Mathur, J. N.; Murali, M. S.; Nash, K. L. Actinide Partitioning─a Review. Solvent Extr. Ion Exch. 2001, 19 (3), 357– 390, DOI: 10.1081/SEI-100103276Google Scholar61https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXksVGitro%253D&md5=100b862a9347cf8173166368c7b6c681Actinide partitioning-a reviewMathur, J. N.; Murali, M. S.; Nash, K. L.Solvent Extraction and Ion Exchange (2001), 19 (3), 357-390CODEN: SEIEDB; ISSN:0736-6299. (Marcel Dekker, Inc.)A review, with 123 refs., is given. Reagents and methods that were developed during the past 20 yr for hydrometallurgical partitioning of actinides from different types of transuranium (TRU) wastes and dissolved fuels are reviewed. Emphasis is placed on the extn. performance of the fully-optimized reagents rather than on the structural iterations that were undertaken (and in some cases are still being conducted) to identify the optimum species. Particular attention is paid to sepn. processes that were demonstrated in batch and counter-current solvent extn., and batch and column mode extn. chromatog. The salient features of the various techniques and reagents for actinide recycle are compared. Sections of the review focus on neptunium behavior in hydrometallurgy and on characterization of those reagents best suited to the sepn. of trivalent actinides from fission product lanthanides. Selected flowsheets that were reported for the sepn. and recovery of actinides from TRU wastes are presented.
- 62Nash, K. L. The Chemistry of TALSPEAK: A Review of the Science. Solvent Extr. Ion Exch. 2015, 33 (1), 1– 55, DOI: 10.1080/07366299.2014.985912Google Scholar62https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitVyjsrnN&md5=8d8bc72079971782c7be4b84a9465f42The Chemistry of TALSPEAK: A Review of the ScienceNash, Kenneth L.Solvent Extraction and Ion Exchange (2015), 33 (1), 1-55CODEN: SEIEDB; ISSN:0736-6299. (Taylor & Francis, Inc.)The TALSPEAK Process (Trivalent Actinide Lanthanide Sepn. with Phosphorus-Reagent Extn. from Aq. Komplexes) was originally developed at Oak Ridge National Lab. by B. Weaver and F. A. Kappelmann in the 1960s. It was envisioned initially as an alternative to the TRAMEX process (selective extn. of trivalent actinides by tertiary or quaternary amines over fission product lanthanides from concd. LiCl solns.). TALSPEAK proposed the selective extn. of trivalent lanthanides away from the actinides, which are retained in the aq. phase as aminopolycarboxylate complexes. After several decades of research and development, the conventional TALSPEAK process (based on di-(2-ethylhexyl) phosphoric acid (extractant) in 1,4-di-isopropylbenzene (diluent) and a concd. lactate buffer contg. diethylenetriamine-N,N,N',N",N"-pentaacetic acid (actinide-selective holdback reagent)) has become a widely recognized benchmark for advanced aq. partitioning of the trivalent 4f/5f elements. TALSPEAK aq. chem. has also been utilized to selectively strip actinides (Reverse TALSPEAK) with some notable success. Under ideal conditions, conventional TALSPEAK separates Am3+ from Nd3+ (the usual limiting pair) with a single-stage sepn. factor of about 100; both lighter and heavier lanthanides are more completely sepd. from Am3+. Despite this apparent efficiency, TALSPEAK has not seen enthusiastic adoption for advanced partitioning of nuclear fuels at process scale for two principle reasons: first, all adaptations of TALSPEAK chem. to process scale applications require rigid pH control within a narrow range of pH, and second, phase-transfer kinetics are often slower than ideal. To compensate for these effects, high concns. of the buffer (0.5-2 M H/Na lactate) are required. Acknowledgement of these complications in TALSPEAK process development has inspired significant research activities dedicated to improving understanding of the basic chem. that controls TALSPEAK (and related processes based on the application of actinide-selective holdback reagents). In the following report, advances in understanding of the fundamental chem. of TALSPEAK that have been reported during the past decade will be reviewed and discussed.
- 63Su, L.-L.; Wu, Q.-Y.; Wang, C.-Z.; Lan, J.-H.; Shi, W.-Q. Heterocyclic Ligands with Different N/O Donor Modes for Am(III)/Eu(III) Separation: A Theoretical Perspective. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c03229Google ScholarThere is no corresponding record for this reference.
- 64Valerio, L. R.; Hakey, B. M.; Leary, D. C.; Stockdale, E.; Brennessel, W. W.; Milsmann, C.; Matson, E. M. Synthesis and Characterization of Isostructural Th(IV) and U(IV) Pyridine Dipyrrolide Complexes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04391Google ScholarThere is no corresponding record for this reference.
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Jordan F. Corbey
Jordan F. Corbey earned her B.S. in Chemistry (2010) from Eastern Washington University and her Ph.D. in Chemistry (2015) from the University of California, Irvine, where she studied air-sensitive rare-earth and f-element coordination complexes under Prof. William J. Evans. Dr. Corbey is currently a staff scientist at Pacific Northwest National Laboratory in Richland, WA, where her research focuses on the synthesis and analysis of radioactive materials for national security missions.
Conrad A. P. Goodwin
Conrad A. P. Goodwin undertook his Ph.D. (2013–2017) at the University of Manchester, studying low-coordinate rare-earth and actinide coordination chemistry using sterically demanding bis-silylamide ligands under Prof. David P. Mills. He followed his graduate work with a brief postdoctoral position at the University of Manchester working on organometallic SMMs and then a J. Robert Oppenheimer Distinguished Postdoctoral Research Fellowship (2018–2021) at Los Alamos National Laboratory under Dr Andrew J. Gaunt. Dr. Goodwin is now a Royal Society University Research Fellow at the University of Manchester, where his group researches the physicochemical properties of rare-earth and actinide complexes with low and high oxidation states.
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- 8Abergel, R. J.; Kozimor, S. A. Innovative f-Element Chelating Strategies. Inorg. Chem. 2020, 59 (1), 4– 7, DOI: 10.1021/acs.inorgchem.9b035838https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXisV2rtb%252FM&md5=22b773416be8f339e3612d64135f0413Innovative f-Element Chelating StrategiesAbergel, Rebecca J.; Kozimor, Stosh A.Inorganic Chemistry (2020), 59 (1), 4-7CODEN: INOCAJ; ISSN:0020-1669. (American Chemical Society)There is no expanded citation for this reference.
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- 10Woen, D. H.; Evans, W. J. Expanding the +2 Oxidation State of the Rare-Earth Metals, Uranium, and Thorium in Molecular Complexes. Handbook on the Physics and Chemistry of Rare Earths; Elsevier, 2016; Vol. 50, pp 337– 394.There is no corresponding record for this reference.
- 11Windorff, C. J.; Chen, G. P.; Cross, J. N.; Evans, W. J.; Furche, F.; Gaunt, A. J.; Janicke, M. T.; Kozimor, S. A.; Scott, B. L. Identification of the Formal + 2 Oxidation State of Plutonium: Synthesis and Characterization of {PuII[C5H3(SiMe3)2]3}−. J. Am. Chem. Soc. 2017, 139 (11), 3970– 3973, DOI: 10.1021/jacs.7b0070611https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXjsVCgt7s%253D&md5=6d6c5f8701e43a2a1666f4d5c92111b6Identification of the Formal +2 Oxidation State of Plutonium: Synthesis and Characterization of {Pu(II)[C5H3(SiMe3)2]3}-Windorff, Cory J.; Chen, Guo P.; Cross, Justin N.; Evans, William J.; Furche, Filipp; Gaunt, Andrew J.; Janicke, Michael T.; Kozimor, Stosh A.; Scott, Brian L.Journal of the American Chemical Society (2017), 139 (11), 3970-3973CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Over 70 years of chem. studies showed that Pu exhibits some of the most complicated chem. in the periodic table. Six Pu oxidn. states were unambiguously confirmed (0 and +3 to +7), and four different oxidn. states can exist simultaneously in soln. The authors report a new formal oxidn. state for Pu, Pu2+ in [K(2.2.2-cryptand)][Pu(II)Cp''3], Cp'' = C5H3(SiMe3)2. The synthetic precursor Pu(III)Cp''3 is also reported, comprising the 1st structural characterization of a Pu-C bond. Absorption spectroscopy and DFT calcns. indicate that the Pu2+ ion has predominantly a 5f6 electron configuration with some 6d mixing.
- 12Su, J.; Windorff, C. J.; Batista, E. R.; Evans, W. J.; Gaunt, A. J.; Janicke, M. T.; Kozimor, S. A.; Scott, B. L.; Woen, D. H.; Yang, P. Identification of the Formal + 2 Oxidation State of Neptunium: Synthesis and Characterization of {NpII[C5H3(SiMe3)2]3}1–. J. Am. Chem. Soc. 2018, 140 (24), 7425– 7428, DOI: 10.1021/jacs.8b0390712https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1cXhtVKmsr7N&md5=e6f1d41a27e7e8df053f5b0d59bd40c7Identification of the Formal +2 Oxidation State of Neptunium: Synthesis and Structural Characterization of {NpII[C5H3(SiMe3)2]3}1-Su, Jing; Windorff, Cory J.; Batista, Enrique R.; Evans, William J.; Gaunt, Andrew J.; Janicke, Michael T.; Kozimor, Stosh A.; Scott, Brian L.; Woen, David H.; Yang, PingJournal of the American Chemical Society (2018), 140 (24), 7425-7428CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)We report a new formal oxidn. state for neptunium in a crystallog. characterizable mol. complex, namely Np2+ in [K(crypt)][NpIICp''3] [crypt = 2.2.2-cryptand, Cp'' = C5H3(SiMe3)2]. D. functional theory calcns. indicate that the ground state electronic configuration of the Np2+ ion in the complex is 5f46d1.
- 13Cloke, F. G. N. Zero oxidation state compounds of scandium, yttrium, and the lanthanides. Chem. Soc. Rev. 1993, 22 (1), 17– 24, DOI: 10.1039/cs993220001713https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK3sXhsF2lurg%253D&md5=fe5c43d028f25dd2f004ae2bff555897Zero oxidation state compounds of scandium, yttrium, and the lanthanidesCloke, F. Geoffrey N.Chemical Society Reviews (1993), 22 (1), 17-24CODEN: CSRVBR; ISSN:0306-0012.A review with 32 refs. on organometallic and coordination compds. of Sc, Y and lanthanides with a valence of 0.
- 14Arnold, P. L.; Cloke, F. G. N.; Hitchcock, P. B.; Nixon, J. F. The First Example of a Formal Scandium(I) Complex: Synthesis and Molecular Structure of a 22-Electron Scandium Triple Decker Incorporating the Novel 1,3,5-Triphosphabenzene Ring. J. Am. Chem. Soc. 1996, 118 (32), 7630– 7631, DOI: 10.1021/ja961253o14https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK28XksVKksb8%253D&md5=e610715ffed9f82319c86fec807f1725The First Example of a Formal Scandium(I) Complex: Synthesis and Molecular Structure of a 22-Electron Scandium Triple Decker Incorporating the Novel 1,3,5-Triphosphabenzene RingArnold, Polly L.; Cloke, F. Geoffrey N.; Hitchcock, Peter B.; Nixon, John F.Journal of the American Chemical Society (1996), 118 (32), 7630-7631CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Cocondensation of Sc vapor with 2,2-dimethylpropylidynephosphine, [Me3CC≡P], affords the triple decker sandwich complex [(η5-tBu2C2P3)Sc(μ-η6:η6-tBu3C3P3)Sc(η5-tBu2C2P3)], which was structurally characterized by x-ray crystallog. The 1st example of a mol. Sc compd. in a formal oxidn. state of 1, this novel triple decker exhibits a remarkably low valence electron-no. of 22. It also displays the 1st structurally characterized example of a triphosphabenzene moiety ligand in a η6 fashion to a metal.
- 15Arnold, P. L.; Cloke, F. G. N.; Nixon, J. F. The first stable scandocene: Synthesis and characterisation of bis(η-2,4,5-tri-tert-butyl-1,3-diphosphacyclopentadienyl)scandium(II). Chem. Commun. 1998, (7), 797– 798, DOI: 10.1039/a800089aThere is no corresponding record for this reference.
- 16Blake, P. C.; Lappert, M. F.; Atwood, J. L.; Zhang, H. The synthesis and characterisation, including X-ray diffraction study, of [Th{η-C5H3(SiMe3)2}3]; the first thorium(III) crystal structure. J. Chem. Soc., Chem. Commun. 1986, 0 (15), 1148– 1149, DOI: 10.1039/C3986000114816https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaL2sXhtVant7s%253D&md5=b456c087ec20113a2280b1205da366f0The synthesis and characterization, including x-ray diffraction study, of [Th{η-C5H3(SiMe3)2}3]; the first thorium(III) crystal structureBlake, Paul C.; Lappert, Michael F.; Atwood, Jerry L.; Zhang, HongmingJournal of the Chemical Society, Chemical Communications (1986), (15), 1148-9CODEN: JCCCAT; ISSN:0022-4936.Redn. of ThL2Cl2 [L = η-1,3-bis(trimethylsilyl)cyclopentadienyl] with Na-K in PhMe gave the title complex I. The structure of I was detd. by x-ray crystallog. I is monomeric in the solid state with the 3 equiv. L groups distributed sym. about the quasi-9-coordinate Th.
- 17Blake, P. C.; Edelstein, N. M.; Hitchcock, P. B.; Kot, W. K.; Lappert, M. F.; Shalimoff, G. V.; Tian, S. Synthesis, properties and structures of the tris(cyclopentadienyl)thorium(III) complexes [Th{η5-C5H3(SiMe2R)2-1,3}3] (R = Me or tBu). J. Organomet. Chem. 2001, 636 (1–2), 124– 129, DOI: 10.1016/S0022-328X(01)00860-9There is no corresponding record for this reference.
- 18Hitchcock, P. B.; Lappert, M. F.; Maron, L.; Protchenko, A. V. Lanthanum does form stable molecular compounds in the + 2 oxidation state. Angew. Chem., Int. Ed. 2008, 47 (8), 1488– 1491, DOI: 10.1002/anie.20070488718https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXisV2ltbk%253D&md5=f1905cc5b699ac01cf4300036f06ad1dLanthanum does form stable molecular compounds in the +2 oxidation stateHitchcock, Peter B.; Lappert, Michael F.; Maron, Laurent; Protchenko, Andrey V.Angewandte Chemie, International Edition (2008), 47 (8), 1488-1491CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Redn. of the LaIII tricyclopentadienide complex [LaCp"3] (Cp" = η5-1,3-(SiMe3)2C5H3) by K and [18]crown-6 or [2,2,2]cryptand produced thermally stable mononuclear cryst. lanthanate(II) salts. The La +2 oxidn. state in these complexes was confirmed both in soln. (EPR) and the solid state (EPR, SQUID, x-ray diffraction) and was supported by a computational study.
- 19Rice, N. T.; Popov, I. A.; Russo, D. R.; Bacsa, J.; Batista, E. R.; Yang, P.; Telser, J.; La Pierre, H. S. Design, Isolation, and Spectroscopic Analysis of a Tetravalent Terbium Complex. J. Am. Chem. Soc. 2019, 141 (33), 13222– 13233, DOI: 10.1021/jacs.9b0662219https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhsVGku7%252FI&md5=923fd66ea05faf580d6272d72dc06cc9Design, Isolation, and Spectroscopic Analysis of a Tetravalent Terbium ComplexRice, Natalie T.; Popov, Ivan A.; Russo, Dominic R.; Bacsa, John; Batista, Enrique R.; Yang, Ping; Telser, Joshua; La Pierre, Henry S.Journal of the American Chemical Society (2019), 141 (33), 13222-13233CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Synthetic strategies to yield mol. complexes of high-valent lanthanides, other than the ubiquitous Ce4+ ion, are exceptionally rare, and thorough, detailed characterization in these systems is limited by complex lifetime and reaction and isolation conditions. The synthesis of high-symmetry complexes in high purity with significant lifetimes in soln. and solid-state are essential for detg. the role of ligand-field splitting, multi-configurational behavior, and covalency in governing the reactivity and phys. properties of these potentially technol. transformative tetravalent ions. Authors report the synthesis and phys. characterization of an S4 sym., four-coordinate tetravalent terbium complex, [Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4] (where Et is Et and tBu is tert-butyl). The ligand field in this complex is weak and the metal-ligand bonds sufficiently covalent so that the tetravalent terbium ion is stable and accessible via a mild oxidant from the anionic, trivalent, terbium precursor, [(Et2O)K][Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4]. The significant stability of the tetravalent complex enables its thorough characterization. The step-wise development of the supporting ligand points to key ligand control elements for further extending the known tetravalent lanthanide ions in mol. complexes. Magnetic susceptibility, ESR spectroscopy, x-ray absorption near-edge spectroscopy (XAS), and d. functional theory studies indicate a 4f7 ground state for [Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4] with considerable zero-field splitting: demonstrating that magnetic, tetravalent lanthanide ions engage in covalent metal-ligand bonds. This result has significant implications for the use of tetravalent lanthanide ions in magnetic applications since the obsd. zero-field splitting is intermediate between that obsd. for the trivalent lanthanides and for the transition metals. The similarity of the multi-configurational behavior in the ground state of [Tb(NP(1,2-bis-tBu-diamidoethane)(NEt2))4] (measured by Tb L3-edge XAS) to that obsd. in TbO2 implicates ligand control of multi-configurational behavior as a key component of the stability of the complex.
- 20Gompa, T. P.; Ramanathan, A.; Rice, N. T.; La Pierre, H. S. The chemical and physical properties of tetravalent lanthanides: Pr, Nd, Tb, and Dy. Dalton Trans. 2020, 49 (45), 15945– 15987, DOI: 10.1039/D0DT01400A20https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXpvValsLw%253D&md5=7c9572fd5551a7e664a0ae23acd4c3f4The chemical and physical properties of tetravalent lanthanides: Pr, Nd, Tb, and DyGompa, Thaige P.; Ramanathan, Arun; Rice, Natalie T.; La Pierre, Henry S.Dalton Transactions (2020), 49 (45), 15945-15987CODEN: DTARAF; ISSN:1477-9226. (Royal Society of Chemistry)A review. The fundamental redox chem. and valence electronic structure of the lanthanides in mol. complexes and extended solids continues to be a fertile area of research. The contemporary understanding of the accessible oxidn. states of the lanthanide elements and the variability in their electronic structure is the result of several paradigm shifts. While the lanthanide elements have already found widespread use in tech. and consumer applications, the continued reevaluation of basic redox properties is a central chem. concern to establish a more complete description of periodic properties. This fundamental understanding of valence electronic structure as it is derived from oxidn. state and coordination environment is essential for the continued development of lanthanides in quantum information science and quantum materials research. This review presents the chem. and phys. properties of tetravalent lanthanide ions in extended solids and mols. with a focus on the elements apart from cerium: praseodymium, neodymium, terbium, and dysprosium.
- 21Palumbo, C. T.; Zivkovic, I.; Scopelliti, R.; Mazzanti, M. Molecular Complex of Tb in the + 4 Oxidation State. J. Am. Chem. Soc. 2019, 141 (25), 9827– 9831, DOI: 10.1021/jacs.9b0533721https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhtFaqs7bI&md5=174c3cd4d152142e3b1520c0b266679aMolecular Complex of Tb in the +4 Oxidation StatePalumbo, Chad T.; Zivkovic, Ivica; Scopelliti, Rosario; Mazzanti, MarinellaJournal of the American Chemical Society (2019), 141 (25), 9827-9831CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Lanthanides (Ln) usually occur in the +3, or more recently the +2, oxidn. states. The only example of an isolated mol. Ln4+ so far remains Ce4+. Here authors show that the +4 oxidn. state is also accessible in a mol. compd. of terbium as demonstrated by oxidn. of the tetrakis(siloxide)terbium(III) ate complex, [KTb(OSi(OtBu)3)4], 1-Tb, with the tris(4-bromophenyl)amminium oxidant, [N(C6H4Br)3][SbCl6], to afford the Tb4+ complex [Tb(OSi(OtBu)3)4], 2-Tb. The solid state structures of 1-Tb and 2-Tb were detd. by x-ray crystallog., and the presence of Tb4+ was unambiguously confirmed by ESR and magnetometry. Complex 2-Tb displays a similar voltammogram to the Ce4+ analog but with redox events that are about 1 V more pos.
- 22Willauer, A. R.; Palumbo, C. T.; Fadaei-Tirani, F.; Zivkovic, I.; Douair, I.; Maron, L.; Mazzanti, M. Accessing the + IV Oxidation State in Molecular Complexes of Praseodymium. J. Am. Chem. Soc. 2020, 142 (12), 5538– 5542, DOI: 10.1021/jacs.0c0120422https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXktlOhs7g%253D&md5=f2222a8fbe3d3f246e223a2763e3fb52Accessing the +IV Oxidation State in Molecular Complexes of PraseodymiumWillauer, Aurelien R.; Palumbo, Chad T.; Fadaei-Tirani, Farzaneh; Zivkovic, Ivica; Douair, Iskander; Maron, Laurent; Mazzanti, MarinellaJournal of the American Chemical Society (2020), 142 (12), 5538-5542CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)Out of the 14 lanthanide (Ln) ions, mol. complexes of Ln(IV) were known only for cerium and more recently terbium. Here we demonstrate that the +IV oxidn. state is also accessible for the large praseodymium (Pr) cation. The oxidn. of the tetrakis(triphenysiloxide) Pr(III) ate complex, [KPr(OSiPh3)4(THF)3], 1-PrPh, with [N(C6H4Br)3][SbCl6], affords the Pr(IV) complex [Pr(OSiPh3)4(MeCN)2], 2-PrPh, which is stable once isolated. The solid state structure, UV-visible spectroscopy, magnetometry, and cyclic voltammetry data along with the DFT computations of the 2-PrPh complex unambiguously confirm the presence of Pr(IV).
- 23Evans, W. J. Advances in f element reductive reactivity as a paradigm for expanding lanthanide and actinide science and technology. J. Alloys Compd. 2009, 488 (2), 493– 510, DOI: 10.1016/j.jallcom.2009.02.018There is no corresponding record for this reference.
- 24Evans, W. J. Tutorial on the role of cyclopentadienyl ligands in the discovery of molecular complexes of the rare-earth and actinide metals in new oxidation states136†. Organometallics 2016, 35 (18), 3088– 3100, DOI: 10.1021/acs.organomet.6b0046624https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XhsFSjurnN&md5=afd9bc63ec9b7bc8cfb0707fde50d036Tutorial on the Role of Cyclopentadienyl Ligands in the Discovery of Molecular Complexes of the Rare-Earth and Actinide Metals in New Oxidation StatesEvans, William J.Organometallics (2016), 35 (18), 3088-3100CODEN: ORGND7; ISSN:0276-7333. (American Chemical Society)A review. This tutorial is based on the award address for the 2015 American Chem. Society Award in Organometallic Chem. sponsored by the Dow Chem. Company, Midland, Michigan. A fundamental aspect of any element is the range of oxidn. states accessible for useful chem. This tutorial describes the recent expansion of the no. of oxidn. states available to the rare earth and actinide metals in mol. complexes that has resulted through organometallic chem. involving the cyclopentadienyl ligand. These discoveries demonstrate that the cyclopentadienyl ligand, which has been a key component in the development of organometallic chem. since the seminal discovery of ferrocene in the 1950s, continues to contribute to the advancement of science. Background information on the rare earth and actinide elements is presented as well as the sequence of events that led to these unexpected developments in the oxidn. state chem. of these metals.
- 25Wedal, J. C.; Evans, W. J. A Rare-Earth Metal Retrospective to Stimulate All Fields. J. Am. Chem. Soc. 2021, 143 (44), 18354– 18367, DOI: 10.1021/jacs.1c0828825https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3MXit1ygu73L&md5=4e94a23152b1b616add0c6f3d32fa65bA Rare-Earth Metal Retrospective to Stimulate All FieldsWedal, Justin C.; Evans, William J.Journal of the American Chemical Society (2021), 143 (44), 18354-18367CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)A review. Formulating insightful questions and expts. is crucial to the advancement of science. The purpose of this Perspective is to encourage scientists in all areas of chem. to ask more "What if" questions: What if we tried this expt. What if we used these conditions. What if that idea is not correct. To stimulate this thinking, a retrospective anal. of a specific field, in this case rare-earth metal chem., is presented that describes the "What if" questions that could have and should have been asked earlier based on our current knowledge. The goal is to provide scientists with a historical perspective of discovery that exemplifies how previous views in chem. were often narrowed by predominant beliefs in principles that were incorrect. The same situation is likely to exist today, but we do not realize the limitations! Hopefully, this anal. can be used as a springboard for posing important "What if" questions that should be asked right now in every area of chem. research.
- 26Kosloski-Oh, S. C.; Knight, K. D.; Fieser, M. E. Enhanced Control of Isoprene Polymerization with Trialkyl Rare Earth Metal Complexes through Neutral Donor Support. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c03161There is no corresponding record for this reference.
- 27Guo, D.; Hong, D.; Huang, Z.; Zhou, S.; Zhu, X.; Wang, S. Reactivity of Rare Earth Metal Alkyl Complexes with Nitriles or Isonitrile: Versatile Ways toward Multiply Functionalized β-Diketiminato, (Iso)indolyl, and Imidazolyl Chelating Rare Earth Metal Complexes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04079There is no corresponding record for this reference.
- 28Pan, F.; Weinert, B.; Dehnen, S. Effect of La3+ on the Formation of Endohedral Zintl Clusters Featuring In/Bi Shells. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.4c00192There is no corresponding record for this reference.
- 29Goodwin, C. A. P. What is a Sandwich Complex?. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.4c00243There is no corresponding record for this reference.
- 30Corner, S. C.; Gransbury, G. K.; Vitorica-Yrezabal, I. J.; Whitehead, G. F. S.; Chilton, N. F.; Mills, D. P. Synthesis and Magnetic Properties of Bis-Halobenzene Decamethyldysprosocenium Cations. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04106There is no corresponding record for this reference.
- 31Corner, S. C.; Gransbury, G. K.; Vitorica-Yrezabal, I. J.; Whitehead, G. F. S.; Chilton, N. F.; Mills, D. P. Halobenzene Adducts of a Dysprosocenium Single-Molecule Magnet. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04105There is no corresponding record for this reference.
- 32Schwarz, N.; Krätschmer, F.; Suryadevara, N.; Schlittenhardt, S.; Ruben, M.; Roesky, P. W. Synthesis, Structural Characterization, and Magnetic Properties of Lanthanide Arsolyl Sandwich Complexes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c03374There is no corresponding record for this reference.
- 33Chen, Q.-W.; Ding, Y.-S.; Zhu, X.-F.; Wang, B.-W.; Zheng, Z. Substituent Positioning Effects on the Magnetic Properties of Sandwich-Type Erbium(III) Complexes with Bis(trimethylsilyl)-Substituted Cyclooctatetraenyl Ligands. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c03369There is no corresponding record for this reference.
- 34Zhu, Y.; Mahoney, J.; Babson, A. J.; Zhou, Z.; Wei, Z.; Gakiya-Teruya, M.; McNeely, J.; Rogachev, A. Y.; Shatruk, M.; Petrukhina, M. A. Homoleptic Rare-Earth-Metal Sandwiches with Dibenzo[a,e]cyclooctatetraene Dianions. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04249There is no corresponding record for this reference.
- 35Schädle, D.; Litlabø, R.; Meermann-Zimmermann, M.; Thim-Spöring, R.; Schädle, C.; Maichle-Mössmer, C.; Törnroos, K. W.; Anwander, R. Rare-Earth-Metal Methyl and Methylidene Complexes Stabilized by TpR,R′-Scorpionato Ligands─Size Matters. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04422There is no corresponding record for this reference.
- 36Blanes-Díaz, A.; Shohel, M.; Rice, N. T.; Piedmonte, I.; McDonald, M. A.; Jorabchi, K.; Kozimor, S. A.; Bertke, J. A.; Nyman, M.; Knope, K. E. Synthesis and Characterization of Cerium-Oxo Clusters Capped by Acetylacetonate. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02141There is no corresponding record for this reference.
- 37Zgrabik, J. C.; Bhowmick, R.; Eckstrom, F. D.; Harrison, A. R.; Fetrow, T. V.; Blake, A. V.; Vlaisavljevich, B.; Daly, S. R. The Influence of Phosphorus Substituents on the Structures and Solution Speciation of Trivalent Uranium and Lanthanide Phosphinodiboranates. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02773There is no corresponding record for this reference.
- 38Bokouende, S. S.; Kulasekara, D. N.; Worku, S. A.; Ward, C. L.; Kajjam, A. B.; Lutter, J. C.; Allen, M. J. Expanding the Coordination of f-Block Metals with Tris[2-(2-methoxyethoxy)ethyl]amine: From Molecular Complexes to Cage-like Structures. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02752There is no corresponding record for this reference.
- 39Shannon, R. D. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallogr. A 1976, 32 (5), 751– 767, DOI: 10.1107/S0567739476001551There is no corresponding record for this reference.
- 40Boggiano, A. C.; Bernbeck, M. G.; Jiang, N.; La Pierre, H. S. Coordination Modes and Binding Patterns in Lanthanum Phosphoramide Complexes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04521There is no corresponding record for this reference.
- 41Shephard, A. C. G.; Delon, A.; Chevreux, S.; Martinez, A.; Guo, Z.; Deacon, G. B.; Lemercier, G.; McClenaghan, N.; Jonusauskas, G.; Junk, P. C.; Jaroschik, F. Divalent ansa-Octaphenyllanthanocenes: Synthesis, Structures, and EuII Luminescence. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c01062There is no corresponding record for this reference.
- 42Fetrow, T. V.; Cashman, B. K.; Carpenter, S. H.; Janicke, M. T.; Anderson, N. H.; Klamm, B. E.; Mason, H. E.; Tondreau, A. M. Oxidative Dissolution of Lanthanide Metals Ce and Ho in Molten GaCl3. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02774There is no corresponding record for this reference.
- 43Uruburo, C.; Rupasinghe, D. M. R. Y. P.; Gupta, H.; Knieser, R. M.; Lopez, L. M.; Furigay, M. H.; Higgins, R. F.; Pandey, P.; Baxter, M. R.; Carroll, P. J.; Zeller, M.; Bart, S. C.; Schelter, E. J. Metal–Ligand Redox Cooperativity in Cerium Amine-/Amido-Phenolate-Type Complexes. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02411There is no corresponding record for this reference.
- 44Gremillion, A. J.; Ross, J.; Yu, X.; Ishtaweera, P.; Anwander, R.; Autschbach, J.; Baker, G. A.; Kelley, S. P.; Walensky, J. R. Facile Oxidation of Ce(III) to Ce(IV) Using Cu(I) Salts. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04337There is no corresponding record for this reference.
- 45Rinehart, J. D.; Fang, M.; Evans, W. J.; Long, J. R. A N23- radical-bridged terbium complex exhibiting magnetic hysteresis at 14 K. J. Am. Chem. Soc. 2011, 133 (36), 14236– 14239, DOI: 10.1021/ja206286h45https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhtVGjtbjF&md5=f239373765668d7ca490e1fa63b55f32A N23- Radical-Bridged Terbium Complex Exhibiting Magnetic Hysteresis at 14 KRinehart, Jeffrey D.; Fang, Ming; Evans, William J.; Long, Jeffrey R.Journal of the American Chemical Society (2011), 133 (36), 14236-14239CODEN: JACSAT; ISSN:0002-7863. (American Chemical Society)The synthesis, crystal structures and magnetic properties of three new N23- radical-bridged dilanthanide complexes, [K(18-crown-6)(THF)2]{[(Me3Si)2N]2(THF)Ln}2(μ-η2:η2-N2)·nTHF (Ln = Tb, Ho, Er; n = 0, 2, 2, resp.), are reported. All three display signatures of single-mol.-magnet behavior, with the terbium congener exhibiting magnetic hysteresis at 14 K and a 100 s blocking temp. of 13.9 K. Synergizing the strong magnetic anisotropy of terbium(III) with the effective exchange-coupling ability of the N23- radical can create the hardest mol. magnet discovered to date. Through comparisons with nonradical-bridged a.c. magnetic susceptibility measurements, the magnetic exchange coupling hinders zero-field fast relaxation pathways, forcing thermally activated relaxation behavior over a much broader temp. range.
- 46Rinehart, J. D.; Fang, M.; Evans, W. J.; Long, J. R. Strong exchange and magnetic blocking in N23– radical-bridged lanthanide complexes. Nat. Chem. 2011, 3 (7), 538– 542, DOI: 10.1038/nchem.1063There is no corresponding record for this reference.
- 47Delano, F. I. V.; Deshapriya, S.; Demir, S. Guanidinate Yttrium Complexes Containing Bipyridyl and Bis(benzimidazolyl) Radicals. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.4c00006There is no corresponding record for this reference.
- 48Morss, L. R.; Edelstein, N. M.; Fuger, J. The Chemistry of the Actinide and Transactinide Elements; Springer: Dordrecht, The Netherlands, 2011. DOI: 10.1007/978-94-007-0211-0 .There is no corresponding record for this reference.
- 49Ordoñez, O.; Yu, X.; Wu, G.; Autschbach, J.; Hayton, T. W. Quantifying Actinide–Carbon Bond Covalency in a Uranyl–Aryl Complex Utilizing Solution 13C NMR Spectroscopy. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c02440There is no corresponding record for this reference.
- 50Li, T.; Heng, Y.; Wang, D.; Hou, G.; Zi, G.; Ding, W.; Walter, M. D. Uranium versus Thorium: A Case Study on a Base-Free Terminal Uranium Imido Metallocene. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c03356There is no corresponding record for this reference.
- 51Deka, H.; Fridman, N.; Eisen, M. S. Temperature Dependence of the Ring Opening of Cyclopropene Imines on Thorium Metallocenes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04213There is no corresponding record for this reference.
- 52MacGregor, F.; Tarula-Marin, J. L.; Metta-Magaña, A.; Fortier, S. A Metallocene Bis(phosphoranocarbene) of Uranium and a Probe of Its Reactivity with Alcohols. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04565There is no corresponding record for this reference.
- 53Arnold, P. L.; Mansell, S. M.; Maron, L.; McKay, D. Spontaneous reduction and C-H borylation of arenes mediated by uranium(III) disproportionation. Nat. Chem. 2012, 4 (8), 668– 674, DOI: 10.1038/nchem.139253https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XhtVehtr%252FN&md5=d8e8ebaa426599aad1c67fc930ea7a8aSpontaneous reduction and C-H borylation of arenes mediated by uranium(III) disproportionationArnold, Polly L.; Mansell, Stephen M.; Maron, Laurent; McKay, DavidNature Chemistry (2012), 4 (8), 668-674CODEN: NCAHBB; ISSN:1755-4330. (Nature Publishing Group)Transition-metal-arene complexes such as bis(benzene)chromium, Cr(η6-C6H6)2, are historically important to d-orbital bonding theory and have modern importance in org. synthesis, catalysis and org. spintronics. In studies of f-block chem., however, arenes are invariably used as solvents rather than ligands. Here, simple U complexes, UX3 (X = aryloxide, amide), spontaneously disproportionate, transferring an electron and X-ligand, allowing the resulting UX2 to bind and reduce arenes, forming inverse sandwich mols. [X2U(μ-η6:η6-arene)UX2] and a UX4 byproduct. Calcns. and kinetic studies suggest a cooperative small-mol. activation' mechanism involving spontaneous arene redn. as an X-ligand is transferred. These mild reaction conditions allow functionalized arenes such as arylsilanes to be incorporated. The bulky UX3 are also inert to reagents such as boranes that would react with the traditional harsh reaction conditions, allowing the development of a new in situ arene C-H bond functionalization methodol. converting C-H to C-B bonds.
- 54Liddle, S. T. The Renaissance of Non-Aqueous Uranium Chemistry. Angew. Chem., Int. Ed. 2015, 54 (30), 8604– 8641, DOI: 10.1002/anie.20141216854https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtVSju7rL&md5=831c0bb3d55c28b6d7809bb1de201a04The Renaissance of Non-Aqueous Uranium ChemistryLiddle, Stephen T.Angewandte Chemie, International Edition (2015), 54 (30), 8604-8641CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)A review. Prior to the year 2000, nonaq. uranium chem. mainly involved metallocene and classical alkyl, amide, or alkoxide compds. as well as established carbene, imido, and oxo derivs. Since then, there was a resurgence of the area, and dramatic developments of supporting ligands and multiply bonded ligand types, small-mol. activation, and magnetism are reported. This Review (1) introduces the reader to some of the specialist theories of the area, (2) covers all-important starting materials, (3) surveys contemporary ligand classes installed at U, including alkyl, aryl, arene, carbene, amide, imide, nitride, alkoxide, aryloxide, and oxo compds., (4) describes advances in the area of single-mol. magnetism, and (5) summarizes the coordination and activation of small mols., including CO, CO2, nitric oxide, dinitrogen, white phosphorus, and alkanes.
- 55Ryan, A. J.; Angadol, M. A.; Ziller, J. W.; Evans, W. J. Isolation of U(II) compounds using strong donor ligands, C5Me4H and N(SiMe3)2, including a three-coordinate U(II) complex. Chem. Commun. 2019, 55 (16), 2325– 2327, DOI: 10.1039/C8CC08767A55https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXkvVSltQ%253D%253D&md5=d345cf3009e9d25f1ad605d50d2009f9Isolation of U(II) compounds using strong donor ligands, C5Me4H and N(SiMe3)2, including a three-coordinate U(II) complexRyan, Austin J.; Angadol, Mary A.; Ziller, Joseph W.; Evans, William J.Chemical Communications (Cambridge, United Kingdom) (2019), 55 (16), 2325-2327CODEN: CHCOFS; ISSN:1359-7345. (Royal Society of Chemistry)New examples of uranium in the formal +2 oxidn. state have been isolated by redn. of Cptet3U (Cptet = C5Me4H) and U(NR2)3 (R = SiMe3) in the presence of 2.2.2-cryptand (crypt) to produce [K(crypt)][Cptet3U] and [K(crypt)][U(NR2)3], resp. Both complexes have properties consistent with 5f36d1 electron configurations and demonstrate that the U(II) ion can be isolated with electron donating ligands.
- 56Modder, D. K.; Palumbo, C. T.; Douair, I.; Fadaei-Tirani, F.; Maron, L.; Mazzanti, M. Delivery of a Masked Uranium(II) by an Oxide-Bridged Diuranium(III) Complex. Angew. Chem., Int. Ed. 2021, 60 (7), 3737– 3744, DOI: 10.1002/anie.20201347356https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BB3cXis1ShurrK&md5=993958f6e2d6d3d6f4014fe93dc20da1Delivery of a Masked Uranium(II) by an Oxide-Bridged Diuranium(III) ComplexModder, Dieuwertje K.; Palumbo, Chad T.; Douair, Iskander; Fadaei-Tirani, Farzaneh; Maron, Laurent; Mazzanti, MarinellaAngewandte Chemie, International Edition (2021), 60 (7), 3737-3744CODEN: ACIEF5; ISSN:1433-7851. (Wiley-VCH Verlag GmbH & Co. KGaA)Oxide is an attractive linker for building polymetallic complexes that provide mol. models for metal oxide activity, but studies of these systems are limited to metals in high oxidn. states. Herein, authors synthesized and characterized the mol. and electronic structure of diuranium bridged UIII/UIV and UIII/UIII complexes. Reactivity studies of these complexes revealed that the U-O bond is easily broken upon addn. of N-heterocycles resulting in the delivery of a formal equiv. of UIII and UII, resp., along with the uranium(IV) terminal-oxo coproduct. In particular, the UIII/UIII oxide complex effects the reductive coupling of pyridine and two-electron redn. of 4,4'-bipyridine affording unique examples of diuranium(III) complexes bridged by N-heterocyclic redox-active ligands. These results provide insight into the chem. of low oxidn. state metal oxides and demonstrate the use of oxo-bridged UIII/UIII complexes as a strategy to explore UII reactivity.
- 57Modder, D. K.; Scopelliti, R.; Mazzanti, M. Accessing a Highly Reducing Uranium(III) Complex through Cyclometalation. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c03668There is no corresponding record for this reference.
- 58Dan, X.; Du, J.; Zhang, S.; Seed, J. A.; Perfetti, M.; Tuna, F.; Wooles, A. J.; Liddle, S. T. Arene-, Chlorido-, and Imido-Uranium Bis- and Tris(boryloxide) Complexes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04275There is no corresponding record for this reference.
- 59Panak, P. J.; Geist, A. Complexation and Extraction of Trivalent Actinides and Lanthanides by Triazinylpyridine N-Donor Ligands. Chem. Rev. 2013, 113 (2), 1199– 1236, DOI: 10.1021/cr300339959https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3sXhslSqtrw%253D&md5=96ab70f9b40c9a2f1e4a9a5782d83c4dComplexation and Extraction of Trivalent Actinides and Lanthanides by Triazinylpyridine N-Donor LigandsPanak, Petra J.; Geist, AndreasChemical Reviews (Washington, DC, United States) (2013), 113 (2), 1199-1236CODEN: CHREAY; ISSN:0009-2665. (American Chemical Society)A review. The following topics are discussed:Lipophilic Bistriazinylpyridines (BTP); Lipophilic Bistriazinyl Bipyridines (BTBP); Water-Sol. BTP and BTBP; Complexation of An(III) and Ln(III) with BTP and BTBP and structure of the complexes; extn. of the complexes; studies using UV/Vis Spectrophotometry, ESI-MS, NMR methods; thermodn. data and description.
- 60Gelis, A. V.; Lumetta, G. J. Actinide Lanthanide Separation Process─ALSEP. Ind. Eng. Chem. Res. 2014, 53 (4), 1624– 1631, DOI: 10.1021/ie403569e60https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXmsVShsg%253D%253D&md5=5a910eaa3b20a8a625b814895dcdbc83Actinide Lanthanide Separation Process-ALSEPGelis, Artem V.; Lumetta, Gregg J.Industrial & Engineering Chemistry Research (2014), 53 (4), 1624-1631CODEN: IECRED; ISSN:0888-5885. (American Chemical Society)Sepn. of the minor actinides (Am, Cm) from the lanthanides at an industrial scale remains a significant tech. challenge for closing the nuclear fuel cycle. To increase the safety of used nuclear fuel (UNF) reprocessing, as well as reduce assocd. costs, a novel solvent extn. process has been developed. The process allows for partitioning minor actinides, lanthanides, and fission products following uranium/plutonium/neptunium removal, minimizing the no. of sepn. steps, flowsheets, chem. consumption, and waste. This new process, actinide lanthanide sepn. (ALSEP), uses an org. solvent consisting of a neutral diglycolamide extractant, either N,N,N',N'-tetra-(2-ethylhexyl)-diglycolamide (T2EHDGA) or N,N,N',N'-tetraoctyldiglycolamide (TODGA), and an acidic extractant 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH-[EHP]), dissolved in an aliph. diluent (e.g., n-dodecane). The An/Ln coextn. is conducted from moderate-to-strong nitric acid, while the selective stripping of the minor actinides from the lanthanides is carried out using a polyaminocarboxylic acid/citrate buffered soln. at pH anywhere between 3 and 4.5. The extn. and sepn. of the actinides from the fission products is very effective in a wide range of HNO3 concns., and the min. sepn. factors for lanthanide/Am exceed 30 for Nd/Am, reaching >60 for Eu/Am under some conditions. The exptl. results presented here demonstrate the great potential for a combined system, consisting of a neutral extractant such as T2EHDGA or TODGA, and an acidic extractant such as HEH-[EHP], for sepg. the minor actinides from the lanthanides.
- 61Mathur, J. N.; Murali, M. S.; Nash, K. L. Actinide Partitioning─a Review. Solvent Extr. Ion Exch. 2001, 19 (3), 357– 390, DOI: 10.1081/SEI-10010327661https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXksVGitro%253D&md5=100b862a9347cf8173166368c7b6c681Actinide partitioning-a reviewMathur, J. N.; Murali, M. S.; Nash, K. L.Solvent Extraction and Ion Exchange (2001), 19 (3), 357-390CODEN: SEIEDB; ISSN:0736-6299. (Marcel Dekker, Inc.)A review, with 123 refs., is given. Reagents and methods that were developed during the past 20 yr for hydrometallurgical partitioning of actinides from different types of transuranium (TRU) wastes and dissolved fuels are reviewed. Emphasis is placed on the extn. performance of the fully-optimized reagents rather than on the structural iterations that were undertaken (and in some cases are still being conducted) to identify the optimum species. Particular attention is paid to sepn. processes that were demonstrated in batch and counter-current solvent extn., and batch and column mode extn. chromatog. The salient features of the various techniques and reagents for actinide recycle are compared. Sections of the review focus on neptunium behavior in hydrometallurgy and on characterization of those reagents best suited to the sepn. of trivalent actinides from fission product lanthanides. Selected flowsheets that were reported for the sepn. and recovery of actinides from TRU wastes are presented.
- 62Nash, K. L. The Chemistry of TALSPEAK: A Review of the Science. Solvent Extr. Ion Exch. 2015, 33 (1), 1– 55, DOI: 10.1080/07366299.2014.98591262https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXitVyjsrnN&md5=8d8bc72079971782c7be4b84a9465f42The Chemistry of TALSPEAK: A Review of the ScienceNash, Kenneth L.Solvent Extraction and Ion Exchange (2015), 33 (1), 1-55CODEN: SEIEDB; ISSN:0736-6299. (Taylor & Francis, Inc.)The TALSPEAK Process (Trivalent Actinide Lanthanide Sepn. with Phosphorus-Reagent Extn. from Aq. Komplexes) was originally developed at Oak Ridge National Lab. by B. Weaver and F. A. Kappelmann in the 1960s. It was envisioned initially as an alternative to the TRAMEX process (selective extn. of trivalent actinides by tertiary or quaternary amines over fission product lanthanides from concd. LiCl solns.). TALSPEAK proposed the selective extn. of trivalent lanthanides away from the actinides, which are retained in the aq. phase as aminopolycarboxylate complexes. After several decades of research and development, the conventional TALSPEAK process (based on di-(2-ethylhexyl) phosphoric acid (extractant) in 1,4-di-isopropylbenzene (diluent) and a concd. lactate buffer contg. diethylenetriamine-N,N,N',N",N"-pentaacetic acid (actinide-selective holdback reagent)) has become a widely recognized benchmark for advanced aq. partitioning of the trivalent 4f/5f elements. TALSPEAK aq. chem. has also been utilized to selectively strip actinides (Reverse TALSPEAK) with some notable success. Under ideal conditions, conventional TALSPEAK separates Am3+ from Nd3+ (the usual limiting pair) with a single-stage sepn. factor of about 100; both lighter and heavier lanthanides are more completely sepd. from Am3+. Despite this apparent efficiency, TALSPEAK has not seen enthusiastic adoption for advanced partitioning of nuclear fuels at process scale for two principle reasons: first, all adaptations of TALSPEAK chem. to process scale applications require rigid pH control within a narrow range of pH, and second, phase-transfer kinetics are often slower than ideal. To compensate for these effects, high concns. of the buffer (0.5-2 M H/Na lactate) are required. Acknowledgement of these complications in TALSPEAK process development has inspired significant research activities dedicated to improving understanding of the basic chem. that controls TALSPEAK (and related processes based on the application of actinide-selective holdback reagents). In the following report, advances in understanding of the fundamental chem. of TALSPEAK that have been reported during the past decade will be reviewed and discussed.
- 63Su, L.-L.; Wu, Q.-Y.; Wang, C.-Z.; Lan, J.-H.; Shi, W.-Q. Heterocyclic Ligands with Different N/O Donor Modes for Am(III)/Eu(III) Separation: A Theoretical Perspective. Inorg. Chem. 2023, DOI: 10.1021/acs.inorgchem.3c03229There is no corresponding record for this reference.
- 64Valerio, L. R.; Hakey, B. M.; Leary, D. C.; Stockdale, E.; Brennessel, W. W.; Milsmann, C.; Matson, E. M. Synthesis and Characterization of Isostructural Th(IV) and U(IV) Pyridine Dipyrrolide Complexes. Inorg. Chem. 2024, DOI: 10.1021/acs.inorgchem.3c04391There is no corresponding record for this reference.