Homo- and heterobimetallic 1,4-divinylphenylene- and naphthalene-1,8-divinyl-bridged diruthenium, diosmium and ruthenium osmium complexes

Heterobimetallic 1,4-divinylphenylene- and 1,8-divinylanthracene-bridged ruthenium/osmium complexes 1-RuOs and 2-RuOs were prepared via stepwise hydroruthenation of the parent dialkynes with first the ruthenium and then the osmium hydride complexes HM(CO)Cl(PiPr3)2. They are compared with their homobimetallic diruthenium and diosmium analogs with respect to their electrochemical and spectroscopic properties. Trends in redox potentials and changes in the vibrational and electronic spectra on oxidation point to strongly delocalized electronic ground states for the radical cations of the homobinuclear complexes and for heterobinuclear 1-RuOs+ but a significant charge localization at the more electron-rich {Os} site for 2-RuOs+ and a generally less efficient coupling of the alkenyl metal moieties to the π-conjugated bridge for the dinuclear 1,8-anthracenediyl complexes. The latter is due to a significant torsion of the alkenyl metal entities as a consequence of steric congestion around the closely spaced alkenyl ruthenium moieties as indicated by X-ray crystallography and by quantum chemical calculations.