the effect of alkyl vs halogen side groups on the stability of boron- heterocyclic carbenes: a computational dft study

The boron-heterocyclic carbenes (bhcs) are divalent five-membered species in which two electron-deficient boron atoms flank the divalent carbon atom. the side groups attached to boron atoms have important role on their stability via singlet- triplet energy gap (∆et-s). in this study the stability of x2bhcs bearing three alkyl groups (x= me, ipr, tbu) is compared to those with halogen (x= f, cl, br) side groups. results show greater ∆et-s for x2bhcs with x= me, ipr, tbu. all structures are bent (puckered). m06/def2- tzvp level of theory is applied for this purpose. all calculations are carried out using guassian 09 program package.