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' = Bu-n) 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)(2)Pt-IV(tpbz)], a presumed intermediate, are isolated from the preparation of [(Ph2C2S2)Pt-II(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 center dotS] and then to [R2C2S center dotS-] - 1e(-) -> [R-2(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 [(dppbO(2))(3)Ni][I-3](2) [dppbO(2) = 1,2-bis(diphenylphosphoryl)benzene] suggests that the steric profile of [(R2C2S2)M(tpbzE(2))] is moderated enough that three could be accommodated as ligands around a metal ion.