GeCl2 cycloaddition reactions to unsaturated organic compounds taking ethylene, buta-1,3-diene, and hexa-1,3,5-triene as examples: a quantum chemical study

Abstract

The cycloaddition reactions of dichlorogermylene GeCl2 to ethylene, buta-1,3-diene, and hexa-1,3,5-triene were studied within the framework of the density functional theory (PBE and B3LYP density functionals) and by the ab initio CBS-QB3 method. The energy characteristics of the reaction of GeCl2 with ethylene were refined and non-empirical quantum chemical calculations of reaction pathways in the GeCl2 + buta-1,3-diene and GeCl2 + hexa-1,3,5-triene systems were carried out for the first time. It was shown that the [2+1] cycloaddition reactions are kinetically hindered and thermodynamically unfavorable, while the [4+1] and [6+1] cycloaddition reactions are characterized by low barriers and result in thermodynamically favorable products. For the [4+1] cycloaddition to buta-1,3-diene and [6+1] cycloaddition to hexa-1,3,5-triene, the most energetically favorable reaction pathways involve a suprafacial and antarafacial approach of reactants, respectively.