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

[Image: see text] Open-ended, singly metalated dithiolene complexes with 1,2,4,5-tetrakis(diphenylphosphino)benzene (tpbz) are prepared either by ligand transfer to [Cl(2)M(tpbz)] from (R(2)C(2)S(2))SnR′(2) (R = CN, R′ = Me; R = Me, R′ = (n)Bu) or by a direct reaction between tpbz and [M(S(2)C(2)R(2))(2)] (M = Ni, Pd, Pt; R = Ph, p-anisyl) in a 1:1 ratio. The formation of dimetallic [(R(2)C(2)S(2))M(tpbz)M(S(2)C(2)R(2))] 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 [(R(2)C(2)S(2))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 [(Ph(2)C(2)S(2))(2)Pt(IV)(tpbz)], a presumed intermediate, are isolated from the preparation of [(Ph(2)C(2)S(2))Pt(II)(tpbz)]. Heterodimetallic [(Ph(2)C(2)S(2))Pt(tpbz)Ni(S(2)C(2)Me(2))] is prepared from [(Ph(2)C(2)S(2))Pt(II)(tpbz)]; its cyclic voltammogram, upon anodic scanning, shows two pairs of closely spaced, but resolved, 1e(–) oxidations corresponding first to [R(2)C(2)S(2)(2)(–)] – 1e(–) → [R(2)C(2)S(•)S(–)] and then to [R(2)C(2)S(•)S(–)] – 1e(–) → [R(2)(C=S)(2)]. The open diphosphine of [(R(2)C(2)S(2))M(tpbz)] can be oxidized to afford open-ended [(R(2)C(2)S(2))M(tpbzE(2))] (E = O, S). Synthesis of the octahedral [(dppbO(2))(3)Ni][I(3)](2) [dppbO(2) = 1,2-bis(diphenylphosphoryl)benzene] suggests that the steric profile of [(R(2)C(2)S(2))M(tpbzE(2))] is moderated enough that three could be accommodated as ligands around a metal ion.