Oxidative addition of CH 2 Cl 2 to neutral dimeric rhodium diphosphine complexes

Neutral dimeric rhodium diphosphine complexes are often employed as catalytic precursors in the presence of the solvent CH2Cl2. The possibility of a collateral reaction between the solvent and the catalytic precursor is never considered as the activation of CH2Cl2 by [Rh2(PP)2 (μ2-Cl)2] complexes is reputed difficult and uncommon. Herein we report the easy formation of three neutral dimeric Rh(III) complexes containing DPPP, DPPB and TangPhos through CH2Cl2 activation as an extension of the few examples reported so far. The system [Rh2 (DPPP)2 (μ2-Cl)2]/CH2Cl2 has been selected for a detailed mechanistic investigation. Kinetic studies based on 31P NMR monitoring combined with metathesis experiments reveal the fundamental role of a 14-electron intermediate [Rh(PP)Cl], which is involved in the CH2Cl2 activation.