METHODS FOR THE SYNTHESIS OF MU-HYDROCARBON TRANSITION-METAL COMPLEXES WITHOUT METAL-METAL BONDS

Transition metal complexes in which hydrocarbons serve as sigma,sigma-, sigma,pi-, or pi,pi-bound bridging ligands are currently of great interest. This review presents efficient and directed syntheses for such compounds, which often have very aesthetic structures. These reactions are among the most important reaction types in modern organometallic chemistry. They can be a useful aid for the synthesis of tailor-made compounds, for example, for models of catalytic processes and, specifically, for the construction of heterometallic compounds. We will discuss reactions of electrophilic complexes with nucleophilic ones, numerous transformations of (functionalized) hydrocarbons with metal complexes, the currently very topical complexes with bridging acetylide and carbide ligands, and organometallic polymers, which can be expected to have interesting and novel materials properties. Chisholm[1] has described the importance of these complexes as follows: ''Central to the development of polynuclear and cluster chemistry are bridging ligands and central to organometallic chemistry are metal-carbon bonds. Thus bridging ligands hold a pivotal role in the development of dinuclear and polynuclear organometallic chemistry''.