AB-INITIO STUDY ON THE STABILITY OF DIAMINOCARBENES

Ab initio calculations at the SCF and correlated levels with triple-zeta doubly polarized basis sets are reported for several diaminocarbenes. Imidazol-2-ylidene, the prototype of the recently isolated stable carbenes, has a significantly higher singlet-triplet splitting than the saturated analogue imidazolin-2-ylidene, which is the origin of its greater thermodynamic stability towards dimerization. The investigated diaminocarbenes have barriers to 1,2-hydrogen shifts of more than 45 kcal/mol and are therefore kinetically stable in this respect.