COMPLEXES OF BORANE(1) [BH] AND HBCN-, HBCO, HBCF- A CALCULATIONAL AND CONCEPTUAL STUDY( )

(BH,C,N)(-), (BH,C,O) and (BH,C,F)(+), designated by the general notat ion (BH,C,X), have been investigated ab initio with a double-zeta bas is set augmented with polarization functions and diffuse functions on the nonhydrogen atoms (DZP(p)). Cyclic and acyclic systems with both B -C and B-X connectivities have been examined for both singlet and trip let states. Geometries were optimized at the MBPT(2) level and single- point energies were obtained at the CCSD, CCSD + T(CCSD) and CCSD(T) l evels. Inclusion of electron correlation affects the equilibrium struc tures and the singlet-triplet gaps. A variety of new species and isome ric types have been identified from this work. For all three systems a cyclic (3)HBCX is most stable. The acyclic triplet is linear for X = O and F and is bent for X = N. The analogous singlet species are stabl e only for X = N and F. At this point, for the acyclic HBXC systems a well defined minimum has been found for only (HBNC-)-H-1. Cyclic sing let and triplet forms exist for HBCN- and HBCO and a pseudo-cyclic for m exists for (HBCF-)-H-1. As an aid in understanding these new species the computational results have been combined with variously derived i ntuition. Suggestions for possible routes to the gas-phase (BH,C,X) c omplexes are made.