Mechanism of the Methylene Transfer Reaction. C−C Activation and Reductive Elimination in One System. A DFT Study

DFT calculations were employed to investigate the methylene transfer reaction mechanism
in a model system related to the experimental Rh/PCP ligand system previously reported
by us. The computationally established mechanism is in accordance with the experimental
results. It was found to be a C−C reductive elimination/C−C oxidative addition sequence in
which the C−C reductive elimination is the rate-determining step. The C−C activation
reaction was found to take place by two different routes; both proceed through the initial
formation of the η2-arene complex 2. In one pathway, C−C activation takes place from an
agostic C−H complex intermediate, and in the other, it occurs from the η2-arene complex
directly. In both intermediates the C−C bond is predirected to the metal center. The
methylene transfer reaction outcome is governed by thermodynamic factors. However,
changing the thermodynamic factors might lead to the reverse methylene transfer reaction
becoming kinetically accessible. The reverse reaction is relevant to the design of a potential
catalytic methylene transfer system.