Homogeneous Catalysis: Organometallic Catalysis and Organocatalysis

Although soluble catalysts have been used in organic chemistry for many years, until the 1960s they involved simple acids, bases, or metal salts. In most cases, the metals were ignored in any mechanistic considerations. For example, copper salts can catalyze the cyclopropanation of olefins using diazo compounds; however, the role of copper was not considered in early mechanisms. Simple soluble nickel and cobalt precursor complexes were used in some industrial processes but were not extensively studied. Heterogeneous catalysis especially for hydrogenation has a much longer history of use in organic synthesis