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

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.