Strong Spin-Orbit Coupling Facilitates C-H Activation in the Reactions of Os+ with CH3F: Theoretical Investigations

Abstract

The relativistic effects are essential for a complete understanding of the reactions involving heavy transition metal cations with hydrocarbons. Despite this, spin-orbit coupling (SOC) along the reaction pathway is rarely considered. In this work, we demonstrate an unusual SOC on the chemical reactivity of a reaction of Os+ with methyl fluoride (CH3F) using density functional theory (DFT), high-level ab initio, and spin-orbit multiconfigurational ab initio methods. With the inclusion of the SO effect in the relevant potential energy surfaces (PESs), C-H bond activation by an Os+ cation occurs readily via almost barrierless (about 2 kcal/mol) PESs of the SO coupled ground state. In contrast, a substantial reaction barrier was observed for C-F bond activation. The calculated results are in line with recent systematic experimental findings for reactions of transition metal cations with CH3F. These results show that the SO effect can facilitate specific bond activation in chemical reactions associated with catalytic transition metal cations.