Fully Reduced and Mixed-Valent Multi-Copper Aggregates Supported by Tetradentate Diamino Bis(thiolate) Ligands

Tetradentate diamino bis(thiolate) ligands (l-N2S2(2−)) with saturated linkages between heteroatoms support fully reduced [(Cu(l-N2S2))2Cu2] complexes that bear relevance as an entry point toward molecules featuring the Cu2ICu2II(μ4-S) core composition of nitrous oxide reductase (N2OR). Tetracopper [(Cu(l-N2(SMe2)2))2Cu2] (l-N2(SMe2H)2 = N1,N2-bis(2-methyl-2-mercaptopropane)-N1,N2-dimethylethane-1,2-diamine) does not support clean S atom oxidative addition but undergoes Cl atom transfer from PhICl2 or Ph3CCl to afford [(Cu(l-N2(SMe2)2))3(CuCl)5], 14. When introduced to Cu(I) sources, the l-N2(SArH)2 ligand (l-N2(SArH)2 = N1,N2-bis(2-mercaptophenyl)-N1,N2-dimethylethane-1,2-diamine), made by a newly devised route from N1,N2-bis(2-fluorophenyl)-N1,N2-dimethylethane-1,2-diamine, ultimately yields the mixed-valent pentacopper [(Cu(l-N2SAr2))3Cu2] (19), which has 3-fold rotational symmetry (D3) around a Cu2 axis. The single CuII ion of 19 is ensconced within an equatorial l-N2(SAr)2(2−) ligand, as shown by 14N coupling in its EPR spectrum. Formation of 19 proceeds from an initial, fully reduced product, [(Cu(l-N2SAr2))3Cu2(Cu(MeCN))] (17), which is C2 symmetric and exceedingly air-sensitive. While unreactive toward chalcogen donors, 19 supports reversible reduction to the all-cuprous state; generation of [19]1– and treatment with S atom donors only return 19 because structural adjustments necessary for oxidative addition are noncompetitive with outer-sphere electron transfer. Oxidation of 19 is marked by intense darkening, consistent with greater mixed valency, and by dimerization in the crystalline state to a decacopper species ([20]2+) of S4 symmetry.

Unit cell and refinement data for compounds 13 and 14. S10 Table S4.
Unit cell and refinement data for polymorphs and pseudopolymorphs of 19. S11 Table S5.
Most of the crystals of the copper complexes used in X-ray diffraction data collections were  The data sets collected with the Smart APEX diffractometer implemented one of the following (JPD718), 14 sets of 326 or 330 frames at 10/sec/frame; [16][PF6]·½17· t BuOMe·2MeCN (JPD776), 14 sets of 326 or 330 frames at 60/sec/frame.
All data were collected under control of either the Bruker APEX2 1a-1d or APEX3 1e-1f software packages. Raw data were reduced to F 2 values using SAINT, 2 and a global refinement of unit cell parameters was performed using ~8000-9950 selected reflections from the full data set, except for 4b (5224 reflections) and 7 (3412 reflections), which were comparatively smaller data sets. For [4a·H2]Cl2 (JPD651), analysis of 2940 reflections having I/σ(I) > 12 and chosen from the full data set with CELL_NOW 3 showed the crystal to belong to the monoclinic system and to be twinned by a 180° rotation about the c* axis. The raw data were processed using the multi-component version of SAINT under control of the two-component orientation file generated by CELL_NOW with an absorption correction was applied using the TWINABS routine. 4 In similar fashion, [18][PF6]·C5H12 (JPD778) was treated as a three-component twin. All other data sets were corrected for absorption on the basis of multiple measurements of symmetry equivalent reflections or by numerical methods with the use of SADABS, 5 as described by Krause et al. 6 All structure solutions were obtained by direct methods using SHELXS 7 or SHELXT, 8 while refinements were accomplished by full-matrix least-squares procedures using SHELXL. 9 Both the SHELXS and SHELXL programs are incorporated into the SHELXTL 10 and APEX2/APEX3 1 software suites.
In all the structures, hydrogen atoms were added in calculated positions and included as riding contributions with isotropic displacement parameters 1.2-1.5 times those of the carbon atoms to which they were attached. In a few instances, minor parts of the molecule/coordination complex were disordered over two positions (e.g., the tert-butyl groups in N 1 ,N 2 -bis(2-( t butylthio)phenyl)- , and the terminal methyl group of the MeCN ligand in 17 (JPD776)), and were treated using the usual split-atom model with a site-occupancy distribution determined as a best-fit by the refinement software. Where present, the PF6 1counteranions were typically disordered, which demanded implementation of interatomic distance restraints in order to achieve stable refinement. Interstitial solvent molecules that were similarly afflicted with disorder were generally handled with what minimal interatomic distance restraints were necessary to accomplish good refinement behavior. In [16][PF6]·½17· t BuOMe·2MeCN small amounts of density remote from the main coordination complex and attributable to partially occupied/disordered solvent sites were removed with the SQUEEZE routine in PLATON. 11 Thermal ellipsoid images have been created with the use of XP, which also is part of the SHELXTL package. All structures were checked for overlooked symmetry and other errors by the checkCIF service provided by the International Union of Crystallography. 12