DFT study of the role of substituents in tin(II) bis(amidoethyl)amine complexes used for ε-caprolactone polymerization

DFT simulations of ring-opening polymerization of ε-caprolactone in the presence of two stannylenes based on bis(2-amidoethyl)amine ligands demonstrated that rate limiting step of the whole process is the nucleophilic attack of a metal initiator with the formation of the tetrahedral carbon from sp² carbon atom of the carboxy group. The presence of electron-withdrawing groups at the terminal nitrogen atoms of the ligands leads to decrease in the activation energy of the rate limiting step.