THE HEAVIER GROUP 14 ANALOGS OF THE BICYCLO[1.1.0]BUTANE RADICAL CATION - A THEORETICAL-STUDY

In view of current interest in bond stretch isomerism in bicyclo[1.1.0]tetrasilane (Si4H6), the radical cations (Si4H6+) in the 2A1 and 2A2 states were investigated by means of ab initio calculations including electron correlation. It is found that the radical cations do not undergo bond stretch isomerism on the same potential energy surface, unlike the case of Si4H6. An interesting finding is that the central Si-Si bridge bonds do not lengthen upon going from Si4H6 to Si4H6+, despite the removal of an electron. Also investigated is the bond stretch isomerism in the still heavier group 14 analogues (X4H6, X = Ge, Sn, and Pb) and their radical cations (X4H6+).