Metal Cluster Topology. 1. Osmium Carbonyl Clusters.
GEORGIA UNIV ATHENS DEPT OF CHEMISTRY
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Important theoretical approaches to metal cluster bonding including the Wade-Mingos skeletal electron pair method, the Teo topological electron count, the King-Rouvray graph theory derived method, and Lauhers extended Huckel calculations are shown to agree in their apparent skeletal electron counts for the most prevalent metal cluster polyhedra including the tetrahedron, the trigonal bipyramid both ordinary and elongated, square pyramid, octahedron, bicapped tetrahedron, pentagonal bipyramid, and capped octahedron. The graph theory derived method is used to treat osmium carbonyl clusters containing from five to eleven osmium atoms. In this connection most osmium carbonyl clusters can be classified into the following types 1 Clusters exhibiting edge-localized bonding containing multiple tetrahedral chambers 2 Capped octahedral clusters derived from osmium carbonyl fragments. Other more unusual osmium carbonyl clusters such as the planar, the Os9 cluster, and the Os11 cluster can also be treated satisfactorily by this methods. The importance of the number of ligands around isoelectronic Os sub n systems in determining the cluster polyhedron is illustrated by the different cluster polyhedra. The tendency for osmium carbonyl clusters frequently to form polyhedra exhibiting edge-localized rather than globally delocalized bonding relates to the facility for osmium carbonyl vertices to contribute more than three internal orbitals to the cluster bonding.
- Organic Chemistry
- Atomic and Molecular Physics and Spectroscopy