MOLECULAR-ORBITAL ANALYSIS OF MONO-CARBIDO-GOLD AND DI-CARBIDO-GOLD CLUSTER COMPOUNDS

The bonding in mono- and di-carbido clusters of gold have been analysed through semi-empirical molecular orbital calculations. The mono-carbido clusters [C(AuPH3)m] are characterised by 12m + 8 valence electrons, and the radial bonding interactions between the carbon and gold atoms predominate. The bonding in related clusters with interstitial boron and nitrogen is also described. In the dicarbido clusters [C2(AuPH3)m] (m = 8, 10 or 12) alternative closed shell electron counts are possible. Clusters with 12m + 10 valence electrons are predicted to be stable and to have short CC distances resulting from CC multiple bonding. In the clusters with 12m + 14 valence electrons the CC distance is likely to be a very sensitive function of the polyhedral geometry. A bonded C2 moiety will be observed only if it is compatible with the formation of AuC bonds of ca 2.0 Å to adjacent gold atoms. Dicarbido-clusters with 12m + 16 electrons are predicted to be unstable relative to monocarbido clusters. © 1990.