A density functional study of trigold oxonium complexes and of their dimerization

The dimerization of trigold oxonium cations has been studied theoretically by means of the all-electron scalar relativistic linear combination of Gaussian-type orbitals density functional (LCGTO-DF) approach. A partial geometry optimization of the model compounds [OAu3](+) and [O(AuPH3)(3)](+) was carried out for these monomers as well as for their dimers, considering various aggregation modes. Additionally, the influence of the steric repulsion of larger phosphine substituents on the structure of the dimer has been examined using a force field method. Reflecting the competition between the Au-Au attraction and the interligand steric repulsion, in agreement with the experimental trends, the dimerization in a locally tetrahedral coordination is favored for the nonligated trigold oxonium cations, whereas a locally rectangular coordination is obtained for the phosphine-ligated complexes.