Low valent metal clusters - an overview

Low valent transition metal cluster chemistry emerges as a major field in organometallic research. Metal clusters exhibit interesting structural, chemical and catalytic properties intermediate between those of mononuclear metal complexes and the multinuclear metals. The opportunities offered by these clusters such as cooperative effect, electron reservoir properties, storehouse of active fragments and heterosite reactivity features are briefly discussed. Other advantages such as mimics of metal surfaces and biomolecules, precursors to heterogeneous catalysts and materials, homogeneous catalysts, and stoichiometric and catalytic reagents in organic synthesis are highlighted. They provide problems of interest in connection with our understanding of structure and bonding. Examples of recent progress in this area show practical promise of preparing new complex organic molecules and inorganic materials by mild and selective methods using these molecules.