Fully Delocalized (Ethynyl)(vinyl)phenylene-Bridged Diruthenium Radical Complexes

Abstract

Diruthenium complexes (X)(dppe)2Ru−C≡C−1,4-C6H4−CH═CH−RuCl(CO)(PiPr3)2 (X = Cl, 1a; X = C≡CPh, 1b) containing an unsymmetrical (ethynyl)(vinyl)phenylene bridging ligand are compared to their symmetrical 1,4-bis(ethynyl)phenylene- and 1,4-divinylphenylene-bridged congeners and their mononuclear alkynyl precursors. Electrochemical and UV/vis/NIR, IR, and EPR spectroscopic studies on the neutral complexes and their various oxidized forms indicate bridging ligand-centered oxidation processes and uniform charge and spin delocalization over both dislike organoruthenium moieties despite differences in their intrinsic redox potentials. Comparison between the chloro and the phenylacetylide-terminated derivatives 1a,b suggests further that the conjugated organometallic π-system extends over the entire unsaturated backbone including the terminal ligand at the alkynyl ruthenium site. This paves the way to even more extended π-conjugated organoruthenium arrays for long-range electronic interactions.