Theoretical studies on the bonding and electron structures of a [Au3Sb6](3-) complex and its oligomers

摘要

Recently an all-metal aromatic sandwich compound of a [Sb3Au3Sb3](3-) ion has been synthesized and characterized experimentally, which indicates that there might exist a variety of stable all-metal sandwich complexes. The intralayer and interlayer chemical bonding interaction in this system plays significant roles in their stability, chemical properties and functionalities. Here we report a systematic theoretical study on the geometries, electronic structures, and chemical bonding of the [Sb3Au3Sb3](3-) ion and its congeners of [X3Au3X3](3-) (X = N, P, As, Sb, Bi, Uup) as well as [X3M3X3](3-) (M, X = Cu, As; Ag, Bi; Au, Sb; Rg, Uup) to understand the special stabilities of these species. Additional studies are also performed on the oligomers [Sb-3(Au3Sb3)(n)](3-) (n = 1-4) to explore whether the sandwich compound can form stable extended systems. Through extensive theoretical analyses, we have shown that among the [Au3X6](3-) (X = N, P, As, Sb, Bi, Uup) species, [Sb3Au3Sb3](3-) is most stable due to superb matching of Sb-3 and Au-3 in both geometric size and fragment orbital energies. The significant stability of the [Au3Sb6](3-) ion is determined by the interlayer (p-d-p)sigma interactions between the vertical Au 5d6s hybrid orbitals of Au-3 and Sb 5p(pi) orbitals of the Sb-3 rings. Each Sb-3 ring demonstrates unique sigma aromaticity, which remains when the complex is extended to oligomers. The results suggest that it is likely that there might exist other stable [A(p)M(p)A(p)](x-) (M = transition metals, A = main group elements, p = 3, 4, 5, ...) sandwich ions and oligomers.