Addition reactions of a polynuclear osmium hydrido compound leading to associative carbonyl substitution and catalytic alkene isomerisation

The ability of H2Os3(CO)10 to undergo addition reactions under mild conditions allows associative CO substitution via isolable intermediates of the type H2Os3(CO)10 (L = CO, PMe2Ph, PPh3 or PhCN) whose spectra and structures are discussed. It is probable that simple addition of alkenes to H2Os3(CO)10 is in part responsible for its facile catalysis of alkene isomerisation. The kinetics of catalytic conversion of terminal to internal alkenes and of allylic alcohols to aldehydes or ketones are reported and discussed. The reactions of H2Os3(CO)10 with allylic halides to give the complexes HOs3X(CO)10 and Os3X2(CO)10 where X = Cl, Br or I are described. Compound H2Os3(CO)10 complies with the 18ρ-rule but nevertheless has a chemistry much like that of coordinatively unsaturated molecules.