Gold cluster complexes bonding

For each cluster size, the few lowest energy equilibrium isomers with molecular adsorption (MA) and two atoms adsorption (TAA) complexes are represented in Fig 8. Most of these structures are planar or near planar. For 4c, 5b, and 5d, only an O atom is not in the plane. Two atom adsorption leads to major structural changes in the gold cluster, particularly for n>5. For example, in the structures 5a, 6a, and 7a, a gold atom breaks the bonds to other Au atoms to form a highly stable linear O-Au-0 unit which bind each 0 atom to one of the remaining Au atoms. On the other hand, molecular adsorption induces only a modest relaxation in the host cluster, and the O2 molecule is attached on top of a Au atom preferably to the bridge position between two Au atoms. 

We conclude that the bond O2-H2 AU5 formed in the complex FA Aus is an example of a nonconventional hydrogen bond. The 5d orbital of the gold atom Au5 in three-gold cluster exhibits a lone-pair character which induces its proton acceptor ability. 

The theoretical treatment of bonding and structure of gold clusters has met with considerable success. For the higher gold dusters, the best predictions are that, for a cluster [AutL, 1]"+ in which the peripheral gold atoms define a closed spherical polyhedron, there will be a closed shell electron configuration when 12x + 6 electrons are present. The structures of complexes... 

The synthetic methods used involve reaction of a cluster anion with [AuCIL], elimination of methane between a cluster hydride and [AuMeL] or addition of LAu+ units to metal-metal bonds. The emphasis here will be on structure and reactions of the complexes. Some examples of mixed gold clusters are given in Table 15, where it can be seen that most work has been on derivatives of clusters of iron, ruthenium and osmium. 

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