C–H Activation of Methyltrioxorhenium by Pincer Iridium Hydride To Give Agile Ir–Re Bimetallic Compounds

Abstract

C–H activation of the CH3 group on methyltrioxorhenium (MTO) by [PNPIrH2]+ (1) affords the bimetallic complex [PNP(H)Ir-μ(CH2)-μ(O)-Re(O)2]+ (2). Investigation of the mechanism revealed that C–H activation is the rate-determining step, and it is preceded by MTO coordination to 1 followed by the release of H2. Reversible isomerization of 2 to [PNP(Me)(CH3CN)Ir-ReO3][PF6] (3) is observed when the solvent is exchanged from noncoordinating to coordinating and vice versa. While the Ir–Re bond in 2 is supported by two bridging ligands, oxo and alkylidene (CH2), the Ir–Re bond in 3 is not supported by any bridging ligands. Hence, the reversibility between these two structural isomers defines the agile nature of the Ir–Re metal–metal bond.