Intermolecular ligand exchange in alkyltin trihalides: semiempirical and density functional theory calculations

Abstract

The mechanism of intermolecular exchange of methyl and ethyl groups for chlorine in CH₃SnCl₃ and C₂H₅SnCl₃, respectively, has been probed through semiempirical (PM3) and density functional theory (B3PW91 and B3LYP) calculations. The reaction is explained by a mechanism involving the formation of the transition state comprising bridging alkyl and chloro groups. The PM3 calculated activation energies are 37.5 and 36.4 kcal mol^-1 while the B3LYP/LANL2DZ calculated activation energies are 50.4 and 41.3 kcal mol^-1 for the methyl and ethyl analogues, respectively. The rate constants calculated at the DFT level are in close agreement with the corresponding experimental values.