Addition and elimination of hydrogen and ligand substitution on triosmium clusters. Kinetics and mechanism |
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Authors: | Lynn M Bavaro Jerome B Keister |
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Institution: | Department of Chemistry, State University of New York at Buffalo, Buffalo, New York 14214 U.S.A. |
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Abstract: | 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(μ3-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. |
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