Bridged versus classical structures in boron-substituted phosphinidenes. A theoretical study of singlet and triplet low energy species

Abstract

Ab initio SCF-CI (6–31G**/MP2 and 6–31G**/MP4) computation of the low-lying singlet and triplet states of PBH 2 ( 1) and PBF 2 ( 2), has been carried out. In the triplet state, both compounds exhibit classical planar C 2v structures, 1t and 2t. In the singlet state, PBH 2 yields the bridged moiety 1s has only stable form, 1s being more stable than 1t. In contrast, PBF 2 yields two stable isomers. The most stable one, 2s has a planar C 2v structure and the second one, 2sa has a planar C s structure, where one F atom has migrated from B to P, via a sizeable activation barrier. In the latter case, 2t is more stable than 2s.