Ab initio study of isomerism, structure, and stability of complex salt molecules of oxo- and thiodihalo- and thiodihydroborates and -aluminates Li[X2MY] (M = B, Al; X=F, Cl, H; Y=O,S)статья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Аннотация:Ab initio calculations of the potential energy surfaces in the vicinity of key structures of X2MY- planar trigonal anions (F2BO-, Cl2BO-, F2BS-, Cl2BS-, F2AlO-, Cl2AlO-, F2AlS-, Cl2AlS-, H2BO-, H2BS-, H2AlO-, and H2AlS-) and their lithium salts Li[X2MY] are performed in terms of the correlated MP4/6-31(+)G**//MP2/6-31G* + ZPE(MP2/(6-31G*) approach. In these structures, the Li+ cation is coordinated to both halogen or hydrogen atoms X in the bidentate mode (structure 1, C-2v(b)), to the chalcogen atom Y in the monodentate mode (structure 2, C-2v(m)), and to the chalcogen atom and one of the X atoms in the bidentate mode (structure 3, C-s(b')). Equilibrium geometric parameters and the frequencies and relative IR intensities of normal vibrational modes of isomers are calculated, and their relative energies and dissociation energies are determined. The bidentate structure 3 is the most stable for all the salts, except aluminates, in which structure 3 transforms without barrier into structure 2 with the deformationally nonrigid Al-O-Li bridge. In all the molecules, the second bidentate structure 1 corresponds to a local minimum lying 12-22 kcal/mol above the global minimum. For various coordination modes of X2MY- anions, their polarization and distortion in the field of the Li+ cation are analyzed; trends in calculated parameters upon the substitution of Al for B, Cl and H for F, S for O, and in other related series are examined.