Open-Ended Metallodithiolene Complexes with the 1,2,4,5-Tetrakis(diphenylphosphino)benzene Ligand: Modular Building Elements for the Synthesis of Multimetal Complexes

Open-ended, singly metalated dithiolene complexes with 1,2,4,5-tetrakis(diphenylphosphino)benzene (tpbz) are prepared either by ligand transfer to [Cl2M(tpbz)] from (R2C2S2)SnR′2 (R = CN, R′ = Me; R = Me, R′ = nBu) or by a direct reaction between tpbz and [M(S2C2R2)2] (M = Ni, Pd, Pt; R = Ph, p-anisyl) in a 1:1 ratio. The formation of dimetallic [(R2C2S2)M(tpbz)M(S2C2R2)] attends these syntheses in modest amounts, but the open-ended compounds are readily separated by silica chromatography. As affirmed by X-ray crystallographic characterization of numerous members of the set, the [(R2C2S2)M(tpbz)] compounds show dithiolene ligands in their fully reduced ene-1,2-dithiolate form conjoined with divalent Group 10 ions. Minor amounts of octahedral [(Ph2C2S2)2PtIV(tpbz)], a presumed intermediate, are isolated from the preparation of [(Ph2C2S2)PtII(tpbz)]. Heterodimetallic [(Ph2C2S2)Pt(tpbz)Ni(S2C2Me2)] is prepared from [(Ph2C2S2)PtII(tpbz)]; its cyclic voltammogram, upon anodic scanning, shows two pairs of closely spaced, but resolved, 1e– oxidations corresponding first to [R2C2S22–] – 1e– → [R2C2S•S–] and then to [R2C2S•S–] – 1e– → [R2(C=S)2]. The open diphosphine of [(R2C2S2)M(tpbz)] can be oxidized to afford open-ended [(R2C2S2)M(tpbzE2)] (E = O, S). Synthesis of the octahedral [(dppbO2)3Ni][I3]2 [dppbO2 = 1,2-bis(diphenylphosphoryl)benzene] suggests that the steric profile of [(R2C2S2)M(tpbzE2)] is moderated enough that three could be accommodated as ligands around a metal ion.


Table of Contents
Procedures for Crystal Growth, Collection and Processing of Diffraction Data, S6-S8 and Solving and Refining of Structures. Computational Details S8-S9 References S9-S10 Table S1.
Unit cell and refinement data for compounds 12, 15, and 16 S13 Table S4.

Table of Contents, Continued
Atomic coordinates for optimized geometry of [(pdt)Pt(tpbz)Ni(mdt)]. S85-S88 2) were comprised of sets of frames, each of 0.5° width in either ω or φ, whose number and scan parameters were determined by the "Strategy" routine in APEX3.
All data were collected under control of either the Bruker SMART, 1 APEX2 2a-2f or APEX3 2g software packages. Raw data were reduced to F 2 values using the SAINT+ 3 or SAINT 4 software, and a global refinement of unit cell parameters was performed using ~3,660-9,990 selected reflections from the full data set. For [(Ph2C2S2)Pt(tpbz)Ni(S2C2Me2)]·2.5(ClCH2CH2Cl), analysis of 1675 reflections having I/σ(I) > 20 and chosen from the full data set with CELL_NOW showed the crystal to belong to the triclinic system and to be twinned by a 180° rotation about c*. The raw data were processed using the multi-component version of SAINT under control of the twocomponent orientation file generated by CELL_NOW, 5 and an absorption correction was applied using the TWINABS routine. 6 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, 7 as described by Krause et al. 8 All structure solutions were obtained by direct methods using SHELXM, 9 SHELXS 10 or SHELXT, 11 while refinements were accomplished by full-matrix least-squares procedures using SHELXL. 12 Both the SHELXS and SHELXL programs are incorporated into the SHELXTL 13 and APEX2/APEX3 2 software suites.
All structure refinements were routine except as noted: (1)  [(Ph2C2S2)2Pt IV (η 2 -tpbz)]·2ClCH2CH2Cl (JPD736), minor disorder for one phenyl group of the tpbz ligand and one Cl atom of the interstitial solvent was observed and similarly treated with split atom models. (4) In the structure of [(Ph2C2S2)Ni(tpbzO2)]·(CH2Cl2), residual density attributed to partially occupied/disordered solvent CH2Cl2 sites was removed with PLATON SQUEEZE 14 (Spek, 2015). Furthermore, five reflections determined to be partially or wholly obscured by the beamstop were omitted from the final refinement. (5) The structure of [(Ph2C2S2)Pt(tpbz)Ni(S2C2Me2)]·2.5(ClCH2CH2Cl) was refined as a two-component twin, and the disordered interstitial ClCH2CH2Cl molecules were refined with constraints approximating ideal geometries. (6) The monoclinic polymorph of [Ni(dppbO2)3][I3]2 showed one triiodide ion (I1···I3) to be disordered over two closely neighboring sites in a 0.703(4)/0.297(4) ratio. The two components of the disorder were refined as rigid rods. Additionally, a small peak appearing to be a partially occupied lattice water site was removed with PLATON SQUEEZE. 14 Seven reflections partially or totally obscured by the beamstop were omitted from the final refinement. 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. 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. 15 Final unit cell data and refinement statistics are collected in Tables S1-S4.

Computational Details
The density functional theory (DFT) calculations were carried out at the supercomputing facility at Tulane University, using the GAUSSIAN-09 package. 16 Geometry optimizations of structures were carried out with no symmetry restrictions beginning with the coordinates of the molecules from X-ray crystallographic data. The geometries were optimized at the Becke, 3-