Thiazetidin-2-ylidenes as four membered N-heterocyclic carbenes: theoretical studies and the generation of complexes with N + center.

Thiazetidin-2-ylidenes have been designed as four membered N-heterocyclic carbenes (NHCs) using quantum chemical studies. These species are smaller analogs of thiazol-2-ylidenes, possess high singlet stability (57 kcal mol -1 ) and large nucleophilicity (3.4 eV). The possible existence of these carbenes has been established by synthesizing and crystalizing compounds with NHC→N + ←(thiazetidin-2-ylidene) coordination bonds.