Dicoordinate boron and phosphorus. HBCN- and HPCN- case study

摘要

Using ab initio calculations we predict anionic and neutral isomers of dicoordinate boron and phosphorus, HE(CN-), HE(CN), (E = B, P). Geometries [at the MBPT(2) /aug-cc-PVTZ level], electron affinities, singlet-triplet (ST) splittings, and PH/BH affinities of CN- (at coupled-clusters level) are presented. For the HBCN- chain the triplet, while for the HPCN- chain the singlet is the around state. The rather small HEB (or HEN) bonding angles in acyclic isomers are explained on the basis of the molecular orbital (MO) picture and 1,3 interactions between hydrogen and carbonitrogen. Both cyanoboryl anion and cyanoboryl radical form also the ring (HBCN- being aromatic with two pi electrons) but for the cyanophosphide the corresponding ring does not constitute a minimum on the potential energy surface. It has four pi electrons and therefore is antiaromatic. Our best electron affinity estimate for HPCN is 2.44 eV, for HBCN it is 0.15 eV, while the corresponding values for the ST splittings of anions are 2.80 and -0.04 eV, respectively. Huge effects of electron correlation on calculated properties of these molecules are discussed. (C) 2001 John Wiley & Sons, Inc. [References: 28]