NHC Complexes of Osmium Clusters: A Structural and Reactivity Study

Abstract

A carbene transfer agent, 1,3-bis-(2,4,6-trimethylphenyl)imidazol-2-ylidene-silver(I)chloride ([IMes]AgCl), was treated with various osmium clusters. Reaction of ([IMes]AgCl) with [Os3(μ-H)2(CO)10] gave [Os3(μ-H)(μ-Cl)(CO)9(IMes)] (1), an osmium N-heterocyclic carbene complex. The reaction of ([IMes]AgCl) with the cluster [Os3(CO)10(CH3CN)2] yielded two products, [Os3(μ-Cl)(CO)10(μ-Ag(IMes)] (2) and [(IMes-H)][Os3(μ-Cl)(CO)10](μ4-Ag)[Os3(μ-Cl)(CO)10] (3). Compound (2) is a heterobimetallic carbene complex resulting from the complete incorporation of ([IMes]AgCl). Transmetalation using [(IMes)AgCl] and the cluster [Os4(μ-H)4(CO)12] in the presence of trimethylamine-N-oxide resulted in the formation of [Os4(μ-H)4(CO)11(n·IMes)] (4), where (n denotes normal carbene bonding, i.e., through C2). [Os4(μ-H)4(CO)10(IMes)2] (5) was formed using the activated cluster [Os4(μ-H)4(CO)10(CH3CN)2] and [(IMes)AgCl]. Compound (5) was found to be sensitive to silica gel column chromatography in the presence of dichlorometha...