Abstract

The argentate trinuclear cluster Ag-3(mu(2)-3,5-(CF3)(2)PyrPy)(3) (3,5-(CF3)(2)PyrPy = 2,2'-pyridylpyrrolide(-) ligand) catalytically promotes the insertion of the carbene of ethyl diazoacetate at room temperature into the C-H bond of a series of alkanes ranging from ethane to hexane, as well as branched and cyclic hydrocarbons. In addition to experimental studies, we also present theoretical studies elucidating the mechanism to C-H activation and functionalization by the transient silver carbene monomer (3,5-(CF3)(2)PyrPy)Ag-(CHCO2Et). On the basis of DFT studies, formation of the silver carbene complex was found to be rate-determining for alkane substrates such as ethane and propane. On the other hand, DFT studies on methane, a substrate that we failed to activate, revealed that carbene insertion into the C-H bond was overall rate-determining. Theoretical analysis of charge flow also shows that the change from separated reagents to the TS involves charge flow from alkane to the silver carbene carbon with the bridging H behaving as a conduit. KIE studies using cyclohexane as a substrate suggest that the product-determining step involves only modest C-H bond lengthening, which can be also represented as a very early transition state with respect to C-H insertion of the carbene.