METALLO-CARBOHEDRENES - CHROMIUM, IRON, AND MOLYBDENUM ANALOGS

The formation of especially stable metal-carbon clusters, which have been designated metallo-carbohedrenes by Castleman and co-workers, has previously been reported for the early transition metals (Ti, Zr, Hf, V). Clusters having the formula M8C12 were recognized as especially stable species which were formed in plasmas containing the metal and a carbon-containing precursor. A similar laser induced plasma technique is employed to synthesize chromium, molybdenum, and iron analogues of these so-called ''met-cars'' clusters and to study their photodissociation behavior. These observations suggest that met-cars cluster formation is a more general phenomenon than previously recognized. While chromium and molybdenum form the ''super-magic'' 8/12 stoichiometry efficiently, met-cars formation competes with other special stoichiometries in the iron clusters. Implications for the bonding properties in met-cars systems are discussed.