Main Group-Transition Element Clusters. Synthesis, Structure and Reactivity

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The main thrust of this project in the Inorganic, Bioinorganic and Organometallic Chemistry Program is the synthesis of new cluster compounds containing boron linked to such transition metals as cobalt and iron. In addition to providing interesting new compounds and contributing to an understanding of the forces which hold large cluster compounds together, the project is expected to provide new routes for the preparation of thin films made up of the cores of the boron-transition metal clusters. Following on the isolation and characterization of a discrete transition metal boride, the first objective is to define the chemistry of six-metal borides and to synthesize related, but presently unknown, systems. Metallacycles will be used as convenient precursors for metal-carbon cages containing boron or aluminum atoms. The facile replacement of the aluminum fragment by other fragments, such as BF, will be investigated as a route to new cages. A transition metal carbido cluster, which has been shown to serve as an exceedingly bulky, strongly pi-donating ligand to boron, will be investigated as a means of stabilizing unusual bonding modes of orbitally-rich ("electron deficient") main group atoms. Since clusters can be coupled or condnsed in a variety of ways to form larger assemblies, the final objective is to demonstrate the usefulness of B-O-B bonds as covalent cluster links; of bipolar cluster ligands in assembling cluster precursors or clusters themselves; and of main group-transition element clusters as precursors to solid thin films made up of the cluster cores.