Rhodium Bis(quinolinyl)benzene Complexes for Methane Activation and Functionalization

A series of rhodium(III) bis(quinolinyl)benzene (bisq^x) complexes was studied as candidates for the homogeneous partial oxidation of methane. Density functional theory (DFT) (M06 with Poisson continuum solvation) was used to investigate a variety of (bisq^x) ligand candidates involving different functional groups to determine the impact on Rh^(III)(bisq^x)-catalyzed methane functionalization. The free energy activation barriers for methane C H activation and Rh–methyl functionalization at 298 K and 498 K were determined. DFT studies predict that the best candidate for catalytic methane functionalization is Rh^(III) coordinated to unsubstituted bis(quinolinyl)benzene (bisq). Support is also found for the prediction that the η^2-benzene coordination mode of (bisq^x) ligands on Rh encourages methyl group functionalization by serving as an effective leaving group for S_N2 and S_R2 attack.