The once-elusive Ni(IV) species is now a potent candidate for challenging organic transformations

Abstract

The past few decades have witnessed a complete renaissance in the field of Ni(IV) catalysis. The properties of Ni(IV) complexes, such as, it undergoes rapid reductive elimination, slower β-hydride eliminations and its involvement in radical processes have permitted a broad range of innovative reaction development involving Ni(IV). The increasingly recognized unique properties of the Ni(IV) complexes have been leveraged to perform organic transformations which were long considered exceptionally complicated. The once elusive Ni(IV) species are now promoting a wide range of organic transformations in a complementary manner to the reactions involving Ni(0) and Ni(II) intermediates. The mechanistic description of a large number of Ni-catalyzed cross-coupling reactions has validated the involvement of high-valent Ni(IV) species in a large number of cross-coupling transformations, thus accessing new synthetic pathways with remarkable chemical activities. This comprehensive review spotlights the pivotal roles of isolated and/or spectroscopically identified Ni(IV) complexes. Amongst many applications, the Ni(IV) complexes have effectively been utilized in (i) C–heteroatom and C[sbnd]C bond formation, (ii) C[sbnd]H bond functionalization

and (iii) N[sbnd]N coupling reactions to forge heterocycles. Herein, we have demonstrated the accomplishments made in the field of organometallic Ni(IV) complexes in the last seven years, with a focus on the most recent and significant developments in the Ni(IV) catalysis emphasizing both synthetic outcomes and mechanisms. © 2022 Elsevier B.V.