Organic & Inorganic Chemistry

Biography

Biography: Ashoka Samuelson

Abstract

Activation of C-H bonds continues to attract significant attention. The interaction of C-H bonds plays an important role in several reactions besides being the key step for activating alkanes. We have carried out computational study of the interaction half-sandwich metal fragments (metal=Re/W/Ru, electron count=d⁶/d⁸), containing linear nitrosyl (NO⁺), carbon monoxide (CO), trifluorophosphine (PF₃), N-heterocyclic carbene (NHC) ligands with alkanes using density functional theory employing the hybrid meta-GGA functional (M06). With d⁶ metal complexes, electron deficiency on the metal improves the formation of stable alkane complexes in the order NHC3+, which corresponds to the electron withdrawing capacity of the ligand. Thus NO⁺ leads to more stable alkane complexes than NHC, a strong electron donor. Stabilization is primarily due to an orbital interaction involving the sigma bond electron density from the alkane flowing to the empty acceptor orbital on the metal. Reactions and C-H activation of the alkane fragment are best facilitated by strong electron donor ligands. These results match most of the experimental results known for CO and PF₃ complexes. Our work suggests a new way of C-H activation, which emphasizes the importance of back donation to the alkane in metal complexes rather than electron donation to the metal.