Unraveling the Amine-Induced Disproportionation Reaction of Perchlorinated Silanes-A DFT Study.

A detailed quantum-chemical study on the amine-induced disproportionation reaction of perchlorinated silanes to neo-Si5 Cl12 is reported. The key intermediate in the resulting mechanistic scenario is a dichlorosilylene amine adduct, which is in tune with recent experimental findings. Yet, at variance with the generally accepted notion of silicon-chain growth by concerted silylene insertion into Si-Cl bonds of lower silanes, the formation of neo-Si5 Cl12 follows more complex pathways. The reactivity is dominated by the Lewis-base character of the dichlorosilylene amine adduct and characterized by three elementary steps that bear close resemblance to the key elementary steps identified earlier for the chloride-induced disproportionation of Si2 Cl6 . NBO and QTAIM analyses of the key reactive species SiCl2 ⋅NMe3 and SiCl3 (-) provide a rationale for these striking similarities.