Silver(I)-Catalyzed Insertion of Carbene into Alkane C–H Bonds and the Origin of the Special Challenge of Methane Activation Using DFT as a Mechanistic Probe

The argentate trinuclear cluster Ag3(μ2-3,5-(CF3)2PyrPy)3 (3,5-(CF3)2PyrPy = 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)2PyrPy)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 ...