Group 14 heavier 1,4-dimetallabenzenes: Influence of Aromaticity, Open-Shell Character and Strain on Small Molecule Activation

Abstract

The influence of the aromaticity, diradical character and strain on the reactivity of Group 14 heavier 1,4-dimetallabenzenes (E = Si, Ge, Sn) has been investigated using quantum-chemical calculations. To this end, the activation reactions of small molecules (dihydrogen and acetylene) promoted by these species have been investigated. It is found that the lighter systems (E = Si and Ge) are significantly more reactive than their 1,4-distannabenzene analogue, despite the latter exhibiting a larger diradical character. According to the Activation Strain Model of reactivity, the reduced reactivity of the heaviest species is directly related to its highly bent, chair-like equilibrium geometry, which must undergo substantial deformation (in comparison with its lighter congeners) to reach the corresponding transition state geometry.