Oriented External Electric-Field Effects on the Activation of Aryl CO Bond in Anisole using Rh(PEP) (E=Al, B, Ga) Catalysts.

Abstract

The present work reports a DFT-based mechanistic investigation of aryl C-O bond activation in anisole catalysed by a Rh-Al pincer-type complex at room temperature. The study is extended to analogues Rh-E complexes based on Group 13 elements (E=B/Ga). Our results show a preference for the heterolytic cleavage pathway over oxidative addition in the C-O bond activation. The calculated barriers range from 16 to 36 kcal/mol, following the order: E=Al<E=Ga<E=B. A strong correlation between the activation barriers and the local electric field (LEF) at the Rh metal centre for the studied Rh-E complexes was observed. Additionally, the ability of Oriented External Electric Field (OEEF) to lower the reaction barrier by applying the OEEF along the direction of electron reorganization, that is, "the reaction axis", was examined. Our results demonstrate the significant effect of applied OEEF on the aryl C-O bond activation in Rh-E systems. Furthermore, the effect of OEEF on the C-O bond activation using modified Rh-E (E=B, Al, or Ga) complexes, in which electronic structure modifications enable a more efficient barrier control by the OEEF, was showcased. Notably, applying a moderate field strength reduces the high reaction barrier for the Rh-B system by approximately 13 kcal/mol.