116079-29-9Relevant academic research and scientific papers
Effects of mixed-metal composition upon the kinetics and thermodynamics of cluster reactions. Preparation of HRu3-nOsn(μ-COMe)(CO)10 and H3Ru3-nOsn (μ3-COMe)(CO)9 (n = 1 or 2) and their relative reactivities toward ligand substitution and reductive elimination of hydrogen
Keister, Jerome B.,Onyeso, Christian C. O.
, p. 2364 - 2372 (2008/10/08)
The new clusters HRu2Os(μ-COMe)(CO)10, H3Ru2Os(μ3-COMe)(CO)9, HRuOs2(μ-COMe)(CO)10, and H3RuOs2(μ3-COMe)(CO)9 have been synthesized and characterized by spectroscopic methods. Retention of the mixed-metal core during hydrogenation of HM2M′(μ-COMe)(CO)10 and carbonylation of H3M2M′(μ3-COMe)(CO)9 proves that cluster fragmentation does not occur during these reactions. Competition experiments were used to determine relative rates of hydrogenation of HM3(μ-COMe)(CO)10 to H3M3(μ3-COMe)(CO)9, attributed to the relative rates of CO dissociation, as M3 = Ru3 (4500) > Ru2Os (1100) > RuOs2 (220) ? Os3 (1) at 343 K. Direct measurements of the rate constants for carbonylation of H3M3(μ3-COMe)(CO)9 to HM3(μ-COMe)(CO)10 give relative rates: M3 = Ru3 (210) > Ru2Os (72) > RuOs2 (38) ? Os3 (1) at 353 K. The similarity of the rates of carbonylation for all clusters having at least one Ru atom, but a greatly reduced rate for the Os3 cluster, suggests that reductive elimination of dihydrogen occurs from a single metal atom in the transition state, even though the hydride ligands bridge two metal atoms in the ground state. Equilibrium constants for hydrogenation and for isomerization of HM2M′-(μ-COMe)(CO)10 were used to obtain estimates of the Ru-H-Ru (408 kJ/mol) and Os-H-Os (425 kJ/mol) bond energies and for the differences in bond energies [E(RuHOs) - E(RuOs)] (299 kJ/mol), [E(Os2(μ-C)) - E(Ru2(μ-C))] (42 kJ/mol), and [E(Os2(μ-C)) - E(RuOs(μ-C))] (24 kJ/mol), based upon the assumptions that [E(M2(μ-C)) - E(M3(μ3-C))] = 0 (M = Ru or Os), [E(Os3(μ3-C)) - E(RuOs2(μ3-C))] = (1/3)[E(Os3(μ3-C)) - E(Ru3(μ3-C))], and [E(Os3(μ3-C)) - E(Ru2Os(μ3-C))] = (2/3)[E(Os3(μ3-C)) - E(Ru3(μ3-C))].
