A computational study on the stability of diaminocarbenes

The 1,2-H shift, 1,2-Me shift, and dimerization reactions of several diamin ocarbenes have been studied using density functional theory and ab initio m ethods. It was observed that the activation energies (E-a) for the dimeriza tion of diaminocarbenes are much smaller than those of 1,2-H shift, 1,2-Me shift and insertion. Dimerization is thus the most likely course of reactio n for diaminocarbenes. The activation energies for the dimerization of diam inocarbenes which exhibit 6 pi-electron delocalization are larger than thos e of the non-aromatic ones. For cyclic diaminocarbenes there is a proportio nal relation between E-a and the singlet-triplet gap (Delta ES-T), i.e., E- a of dimerization is larger as Delta ES-T increases. (C) 2000 Elsevier Scie nce B.V. All rights reserved.