Reaction of boron atoms with ethylene: ab initio study of the borirane radical

Ab initio self-consistent field theory, second-order Møller-Plesset perturbation theory, hybrid density functional theory (B3LYP), coupled cluster theory including single and double excitations and with non-iterative inclusion of triple excitations calculations have been used to examine the structure, vibrational properties and bonding of the borirane radical which has a 2A1 electronic structure. This species is bound by about 40 kcal/mol with respect to the B+C2H4 ground states. For comparison, CCSD calculations have been performed on both the borirane molecule and the Π-complexes for which the electronic structure correlates with the ethylene and boron ground states. The 2B2 Π-complex is bound by about 13 kcal/mol while the 2B1 complex is weakly bound and the 2A1 complex is not bound at all with respect to B+C2H4. Vibrational frequencies and infrared intensities have been calculated at different levels of theory for the borirane radical in order to help its experimental identification.