theoretical study of tetrahydroborates and alanates L(MH4)4, HL(MH4)3, H2L(MH4)2, and H3L(MH4) (L = Al, Sc, Ti, V, Cr; M = B, Al)

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Abstract
The structural and energetic characteristics of the lowest-lying structures for isolated molecules and ions of light-metal boro- and aluminohydrides L(MH4)4, HL(MH4)3, H2L(MH4)2, and H3L(MH4) (L = Al, Sc, Ti, V, Cr; M = B, Al) with different coordination modes of BH 4 − - and AlH 4 − groups were calculated by the perturbation theory (MP2), coupled cluster (CCSD(T)), and density functional theory (B3LYP) methods using the 6-31G*, 6-311+G**, and 6-311++G** basis sets. The results are compared with the computational data obtained at the same level of theory for related complexes L(MH4)3, HL(MH4)2, H2L(MH4), L(MH4)2, and HL(MH4). The preferable coordination modes of the ligands in these complexes are analyzed, and the energies of dissociation with elimination of BH3 (AlH3) molecules and BH 4 − (AlH 4 − ) anions in various series of related hydroborates and hydroaluminates are estimated. The structure and relative stability of classical hydride and (μ-H2)-hydrogen complexes in the H2L (MH4)2 and H3L(MH4) systems are discussed.