Metal Cluster Topology. 3. Platinum Carbonyl Clusters.
GEORGIA UNIV ATHENS DEPT OF CHEMISTRY
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Previously discussed topological models of metal cluster bonding are now extended to the treatment of stacked platinum carbonyl clusters, whose structure and bonding exhibit a variety of new feataures. The stacked triangle cluster dianions Pt3kCO6k2- k2,3,4,5 are best regarded as built from edge-localized bonds with additional Mobius delocalization on both the top and bottom triangles of the stack. These stacked triangles thus appear to be the first examples of stable chemical species having planar rings of atoms exhibiting Mobius rather than untwisted Huckel delocalization. Such Mobius delocalization can naturally arise from the phase changes of appropriated orbitals of each of the platinum atoms in the top and bottom triangles of the stack. The more complicated tetraanion Pt19CO224- can be regarded structurally as a threaded tube in which a Pt15 stack of three pentagons is the tube and a Pt4 chain is the thread. Edge-localized bonding is then seen to occur within both the Pt15 stack 25 edges and the Pt4 thread 3 edges with additional delocalized bonding within the pentagonal pyramidal chambers at each end of the stack. These seemingly rather exotic topological bonding models are consistent with the general principles of metal cluster bonding and reproduce exactly the observed electron counts for the stacked platinum carbonyl clusters.
- Organic Chemistry
- Atomic and Molecular Physics and Spectroscopy