ADDITION AND ELIMINATION OF HYDROGEN AND LIGAND SUBSTITUTION ON TRIOSMIUM CLUSTERS. KINETICS AND MECHANISM.

Article abstract of DOI:10.1016/0022-328X(85)80090-5

The kinetics of the reversible reaction HOs3(μ-COMe)(CO)10 + H2 <*> H3Os3(μ₃-COMe)(CO)9 + CO has been investigated.The reaction of HOs3(μ-COMe)(CO)10 with hydrogen involves dissociation of a CO ligand prior to the rate-determining step, which is proposed to be the oxidative addition of molecular hydrogen.The reaction of H3Os3(μ-COMe)(CO)9 with CO involves rate-limiting hydrogen loss.The equilibrium constant and the competition ratio for hydrogen and CO for the unsaturated intermediate were determined.The mechanism of substitution by AsPh3 on HOs3(μ-COMe)(CO)10 also involves a CO dissociative mechanism.Based upon relative rate constants for CO, AsPh3, and hydrogen addition to HOs3(COMe)(CO)9, CO dissociation and hydrogen addition are proposed to occur at different metal sites.