Coordination of Unsaturated Molecules to Transition Metals

The interaction of unsaturated molecules,–—for example, olefins and acetylenes— with transition metals is of paramount importance for a variety of chemical processes. These processes are stercospecific polymerization of olefin monomers, the production of alcohols, aldehydes in the hydroformylation reaction, hydrogenation reactions, cyclopropanation, isomerizations, hydrocyanation, and many other reactions. The chapter focuses on the coordination of unsaturation molecules to transition metals and the metrical aspects of this interaction as derived from a considerable body of structural data. The broad geometrical features of the interaction between unsaturated molecules and transition metals are now well-defined as a result of a large number of structural studies. In a general way these results can be rationalized by current, crude bonding model. But if the overall understanding of the bonding of unsaturated molecules to transition metals is to be improved, additional experimental and theoretical work needs to be done. On the experimental side, a number of factors must be considered. The diffraction results on a given compound could be improved considerably if the experiment is done at low temperatures so that the smearing effects of thermal motion could be minimized.