This award from the Inorganic, Bioinorganic and Organometallic Chemistry Program is in the general area of metallacarboranechemistry. Metallacarborane compounds are of substantial current interest because of the unusual types of chemical bonds which they illustrate, and are also of practical importance because they are precursors to important ceramics and can be used to synthesize new materials with interesting electrical properties, such as one-dimensional conductors. The major emphasis of the project is the synthesis of extended main group heterocarborane systems that may exhibit interesting structural, electrical and spectral properties. New charge-transfer complexes of main group heterocarboranes will be synthesized and their structures obtained. Of particular interest for these complexes are the factors which influence the slippage of the apical heteroatom, the orientation of ligands bound to this apical heteroatom, and the effect of ligand basicity on cluster bonding and structure. Also to be explored are new areas of chemistry suggested by previous work on the M(II)-inserted closo- and M(IV)-sandwiched commo-carboranes (M=Si and Ge). This will include the synthesis of several multilevel stacked silicon, germanium and mixed silicon/germanium sandwiched complexes and a study of their electrical properties. The final area of heterocarborane chemistry to be explored is direct synthetic approaches to extend, exploit and develop reactions of main group heterocarboranes in which the apical heteroatom undergoes predominantly nonreductive substitution reactions with a variety of main group and transition metals.
