A computational study of the mechanism of chloroalkane dechlorination with Rh(i) complexes

Abstract

This work utilizes density functional theory and the energetic span model to determine steps constituting the catalytic cycle and turnover frequencies, respectively, for C(sp³)–Cl activation and dechlorination by model Rh(I) complexes containing POP-Pincer ligands with the aid of Na salts. The steps in the catalytic cycle with NaHCO₂ as the hydrogen carrier are (i) rotation of the Rh–Cl bond out of the ligand plane, (ii) metal insertion into the C–Cl bond, (iii) formate binding and removal of one Cl as NaCl, (iv) formation and removal of CO₂ from formate-bound Rh, and (v) hydrogenation of the alkyl bound to Rh to form an alkane, followed by Rh–Cl rotation to restore the catalyst resting state. We find that the the turnover-determining states and TOFs for monochloropropane (MCP) dechlorination depend strongly on the hydrogen carrier, with significantly higher TOF for NaH than NaHCO₂. Therefore, NaH may be a promising salt for alkylchloride dechlorination with Rh(I) complexes.