Nickel complexes of NHC and phosphorus ligands in catalyzing CH bond functionalization reactions

Abstract

Organometallic catalysts have made serious inroads to achieve a number of synthetically valuable organic reactions that would otherwise seem impossible to materialize. Despite the enormous success of 4d and 5d metals (e.g., Ir, Pd, Rh) in various catalytic systems in the last several decades, they have made partial headway into this field due to their scarcity and cost-ineffectiveness. To overcome these obstacles, complexes containing relatively abundant, affordable, and more environmentally benign 3d metals, such as iron, nickel, and cobalt are being explored for utility in different organic transformations. Recently various research groups have investigated the prospects of these transition metals in catalyzing the CH bond functionalization reactions. Such reactions enable the synthesis of various biologically active compounds, including the naturally occurring compounds, pharmaceutical drug molecules and agriculturally essential products. These base metals provide a new technique for the formation of CX bonds (X = Carbon or heteroatom) in an extremely controlled and selective way without the requirement of pre-functionalization. This review discusses the detailed synthetic procedures of nickel-catalyzed functionalization of inert CH bonds, in presence of N-heterocyclic carbene ligands and phosphorus-based ligands, thereby forming important organic synthons containing different CX bonds (X = Carbon or heteroatom).