Alkyl-metal and aryl-metal bond chemistry in coordinately unsaturated polynuclear metal complexes

Abstract A new class of coordinately unsaturated polynuclear rhodium and iridium alkyl, benzyl, and aryl derivatives of the form [RM(1,5-cyclooctadiene)]x have been prepared by the reaction of the organolithium reagent with the cyclooctadienemetal chlorides at -78°C. The x-ray crystal structure of [μ-CH3Rh (1,5-cyclooctadiene)]2 is reported. The analogous iridium dimer decomposes by an initial sequence of α-hydrogen abstraction and then reductive elimination of hydrogen to give [μ-CH2Ir(1,5-cyclooctadiene)]2. Formed in high yield by the decomposition of the ethylrhodium complex was [HRh(C8H11)]4, a tetrahedral cluster with face-bridging hydride ligands. Also discussed are the reactivities of the benzyl and phenyl derivatives. Unique reaction pathways for C—H bond activation and scission in this chemistry are delineated.