Beyond conventional N-heterocyclic silylenes: A density functional approach toward structural features and catalytic applications

A new family of heterocyclic silylenes including amino-, phosphino-, oxy-, thio- and alkylsilylenes which enjoy from the stabilizing effect of only one heteroatom are being introduced. The calculated singlet-triplet energy gaps (ΔE _S-T=E _T-E _S) demonstrate the following decreasing trend: (amino≈oxy)>thio>phosphino≈alkyl. The results obtained for aminoalkylsilylenes are compared and contrasted to the well known diaminosilylenes. The reactivity of the species is discussed in terms of nucleophilicity and electrophilicity indices. Amino and phosphino groups can serve as good sites for bulky substitution and hence provide steric protection for silylenes.