Ion pairing in transition-metal organometallic chemistry

An overview of ion pairing in transition metal organometallic chemistry is given. Main group metal and transition metal complex ion pairs are distinguished on the basis of the nature of the metal-ligand bond. Focus is on the effect of ion pairing on the structure and reactivity of transition metal organometallic ion pairs in cases where the counterion still maintains most of its original charge, and consequently does not significantly share electron density with the metal center. The types of reactions covered in which ion pairing plays a critical role include formation and heterolytic splitting of dihydrogen metal complexes, olefin polymerization, and Diels-Alder, hydrogenation, and carbonylation processes.