Nickel-Carbon σ-Bonded Complexes

This chapter documents nickel aryl and alkyl complexes. The complexes are organized by their supporting ligands such as tridentate, bidentate and monodentate ligands. Pincer ligands stabilize a variety of organonickel complexes that have enabled fundamental studies, but often lack catalytic reactivity. A variety of bidentate ligands have found applications in olefin polymerization and cross-coupling reactions. Monodentate NHC and phosphine ligands can support low-coordinate nickel complexes. The past two decades have witnessed the advancements in low-valent, high-valent, and mixed-valent nickel complexes. Monovalent nickel complexes can activate electrophiles to generate radicals, which is relevant to their catalytic reactivity. High-valent nickel complexes can mediate facile reductive elimination to form various bonds. Several monometallic and multimetallic nickel complexes serve as the biomimetic model of nickel-containing metalloenzymes and exhibit relevant reactivity. Ligand redox-activity and metal-ligand cooperativity are common methods for tuning the reactivity of nickel complexes.