Electron localization function studies of the nature of binding in neutralrare-gas containing hydrides: HKrCN, HKrNC, HXeCN, HXeNC, HXeOH, and HXeSH

Neutral rare-gas containing molecules HRgCN (Rg=Kr, Xe), HXeSH and HXeOH ar e investigated by means of topological analysis of the electron localizatio n function (ELF). This analysis explains the type of bonding and delocaliza tion of electron density in chemical systems based on the indirect probabil ity of finding two electrons with the opposite spins. The calculations reve als that all studied species are charge-transfer systems with the approxima te formulas: [HKr](+0.65)[CN](-0.65), [HXe](+0.66)[CN](-0.66), [HXe](+0.45) [SH](-0.45), and [HXe](+0.57)[OH](-0.57). The isomerization process from HR gCN to HRgNC increases the charge separation to 0.72e for Kr and 0.74e for Xe containing molecules. It is shown that the Rg-C, Rg-N, Xe-S, and Xe-O bo nds belong to the unshared electron type and are mainly of the electrostati c origin. The minimum of ELF in the Kr-C and Kr-N linkage, studied at the B 3LYP/6-311++G(2d,2p) computational level, yields relatively high values of about 0.4 and 0.3, respectively. There is a correlation between larger stab ility of HRgCN isomers and an increased exchange of the electron density be tween the lone electron pair of carbon and the nonbonding electron density of xenon: V(C)<---->V(Xe) as compared to smaller V(N)<---->V(Xe) delocaliza tion in less stable HRgNC isomers. The analysis of the CN group reveals the covalent character of the carbon-nitrogen bond, which is confirmed on the basis of presence of the disynaptic valence V(C,N) attractor positioned nea r to nitrogen. The HRgCN --> HRgNC isomerization results in depletion of th e carbon-nitrogen bond V(C,N) and a large saturation of the valence nitroge n basin V(N). (C) 2001 American Institute of Physics.