SMALL CARBORANES AS BUILDING-BLOCKS IN DESIGNED ORGANOMETALLIC SYNTHESIS

Methods are now at hand to permit the systematic construction of multidecker-, multilevel-, and linked-sandwich complexes from transition metals, aromatic hydrocarbon or heterocyclic ligands, and carborane (C2B3) rings. As a consequence of detailed studies of the electronic properties and chemistry of selected building-block complexes, especially those of the type LM(R2C2B3H4R'), where L is C5R5 or an arene and M is a first-, second-, or third-row transition element, the reactivity of such compounds can be adjusted, or "tuned", by attachment of appropriate R' substituents to boron; this allows the controlled synthesis of a variety of types of polymetallic systems which exhibit substantial electron-delocalization. These include triple- and tetradecker complexes, poly(sandwich) species linked via organic units attached at boron or carbon positions, and related systems. This chemistry in turn opens the way to the preparation of extended molecular solid or liquid materials which can be tailored to combine unusual or novel electronic properties with high thermal and oxidative stability.