Electronic and Geometric Structure of the Cluster Compound Au55[P(C6H5)3]12Cl6. A Computational Study

Abstract

Relativistic density functional calculations have been carried out on the model cluster Au55(PH3)12Cl6 assuming a cuboctahedral or an icosahedral Au55 metal core to model the experimentally suggested cluster compound assigned as Au55[P(C6H5)3]12Cl6. Besides the overall shape of the metal core, the study focused on the unresolved issue at which sites the chlorine ligands are attached. The calculations reproduce characteristic interatomic distances within ∼ 2 pm, with the exception of the Au-Cl bonds. Chlorine ligands were calculated to prefer higher coordinated sites whereas the previously postulated on-top coordination at the center of the Au (100) facets of a cuboc-tahedron was found to be unstable. In fact, the present model results suggest an ensemble of several higher coordinated sites. The often assumed cuboctahedral shape of the metal cluster core was determined to be slightly less stable than an approximately icosahedral shape. The calculations allow a rationalization of the difficulties faced in experiments that attempted to discriminate cluster isomers. © 1946 – 2014: Verlag der Zeitschrift für Naturforschung. All rights reserved.