Room-Temperature Methane Activation in Dichloromethane Solutions of [LPtIVR(Me)(H)]+ (R = Me, H; L = Substituted [2.1.1]-(2,6)-Pyridinophanes): DFT Modeling

DFT calculations were used to explore the mechanism of methane reductive elimination from two series of platinum(IV) complexes, (211-X)PtIVMe2H+ and (211-X)PtIVMe(H)2+, where (211-X) is an X-substituted [2.1.1]-(2,6)-pyridinophane and X = H, NO2, BF3–, used as BArF4– salts (for cationic complexes), in dichloromethane solutions. The experimentally determined Gibbs free energies of activation of the reactions of the unsubstituted complexes (X = H) are a good match to the ones calculated by DFT under the assumption of realization of the dissociative mechanism of methane substitution in intermediate σ-methane complexes as the reaction rate-determining step. In this work we predict (i) facile ambient-pressure methane activation in dichloromethane solutions of (211)PtIVMe2H+ and (211)PtIVMe(H)2+ leading to their degenerate methyl fragment exchange with methane and (ii) faster methane reductive elimination reactivity of both their electron-poorer (X = NO2) and electron-richer (X = BF3–) analogues. These results may be useful for the development of low-temperature energy-efficient catalytic transformations of alkanes, including methane.