This page reproduces content from , Base Metals in Catalysis: From Zero to Hero, in Green and Sustainable Medicinal Chemistry, Methods, Tools and Strategies for the 21st Century Pharmaceutical Industry, 2016.
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The industry has gone some way in mitigating the cost and scarcity of catalytic species based on rare metals, through the development of metal reclaiming processes. An alternative strategy to metal reclaiming processes is to shift away from the use of scarce metals to more earth abundant and cheaper base metal catalysts. The major advantages to the use of base metal catalysts, aside from the greater abundance and low cost, include the fact that base metals exhibit low toxicity and are also environmentally benign.
The application of such metals in catalysis has crawled behind the huge advances made by precious metals however; there has been a renewed interest in the challenge in matching or outperforming the high activity and selectivity demonstrated by the platinum group metals, through investigating new ligands and reaction conditions that overcome the unpredictable nature of base metals. First row transition metals are known to readily undergo one electron oxidation state changes, partake in uncontrolled reactions with elemental oxygen and display facile ligand redistribution. In contrast, precious metal catalysis has established a plethora of predictable chemistries based on two electron changes between oxidation states. Base metals such as cobalt, copper, nickel, iron among others are some of the most earth abundant and the nearly limitless supply of iron allows its use on vast reaction scales such as those of the Haber–Bosch ammonia synthesis.
Cobalt, iron and nickel catalysts have been investigated in parallel with palladium catalysts for carbon-carbon bond formation and it has been found that when supported by the appropriate ligands, nickel and cobalt can enable efficient coupling reactions allowing the formal addition of carbon-hydrogen bonds in unsaturated systems.  Iminopyridine ligands have shown promise as privileged ligands in iron catalysis, and have been used in iron-catalysed methodologies for the production of olefin hydrogenation, carbon–carbon and carbon–hetroatom bond formation.