Nickelmediated

Nickel-mediated refers to chemical reactions in which nickel species act as a mediator or catalyst to facilitate bond formation or functionalization. The approach is used across organic, inorganic, and materials chemistry and encompasses catalytic cycles where nickel enables turnover, selectivity, or access to transformations that may be challenging with other metals.

In organic synthesis, nickel-mediated processes include cross-coupling, reductive coupling of electrophiles, and hydrofunctionalization of alkenes. Nickel is especially valued for activating alkyl electrophiles and enabling cross-electrophile couplings, sometimes with photoredox or electrochemical methods, to form C–C and C–heteroatom bonds.

Mechanistically, nickel undergoes oxidation state changes among Ni(0), Ni(I), Ni(II), and Ni(III). Reactions often involve oxidative addition, single-electron transfer or radical capture, transmetalation, and reductive elimination. Radical pathways are common in alkyl-substrate transformations, expanding the scope beyond traditional two-electron steps.

Advantages include earth-abundant nickel, lower cost, and access to new reactivities not always available to palladium catalysts. Limitations include sensitivity to air or moisture, potential for side reactions, and the need for careful ligand and additive selection to control outcomes.

The concept of nickel-mediated transformations has grown since the late 20th century, with ongoing research expanding its scope in complex molecule synthesis and materials science. It remains a dynamic area in catalysis, offering practical alternatives in pharmaceutical, agrochemical, and polymer applications.