Gold-thiolate complexes: A density functional study of geometry and electronic structure

With the help of quantum chemical calculations, we have examined the series of complexes [(H₃PAu)(n)SH]((n-1)+) (n = 1 - 3) as models for recently synthesized gold-thiolate species with PMe₃ and SMe ligands. Using a scalar-relativistic density functional approach, we determined the geometry and the electronic structure, as well as bond energies. Calculated geometries compare well with experimental data of complexes carrying larger phosphine and thiolate ligands. The increasing coordination of the sulfur atom along the series leads to weaker Au-S bonds, while the Au-P bonds strengthen because of the increase of charge. Structure and bonding in this class of complexes can be rationalized by regarding the moiety [AuPR₃]⁺ as σ acceptor in analogy to H⁺ interacting with the p lone pair orbitals of the thiolate group. (C) 2000 Elsevier Science B.V.