Organometallic Chemistry of High‐Valent Ni ( III ) and Ni ( IV ) Complexes

Scrutinizing formally NiIVcenters through the lenses of core spectroscopy, molecular orbital theory, and valence bond theory

“…CCSD(T) and full-CI calculations), and more accurate contributions of ionic congurations, 62 which we nd are To summarize, both VB and high-level MO calculations converge on an identical physical description of the formally Ni IV center of 19; it is a low-valent 3d 8 4s/p 1 Ni I ion. This reinforces the notion that 3d 6 Ni IV is physically unrealistic. Such a conclusion can also be reached on the basis of electronegativity arguments.…”

“…[2][3][4][5] One area of focus has been accessing formally Ni IV species to test the viability of Ni as a replacement metal in reactions that invoke Pd redox couples. 6 These efforts have spurred important discoveries, not only in terms of the rst syntheses of stable complexes bearing formally Ni IV centers, but also of new applications of Ni. For example, Sanford and co-workers 7 reported (Tp)Ni IV (aryl)(CF 3 ) (Tp = trispyrazolylborate) species that undergo formal reductive elimination to generate aryl-CF 3 bonds in high yields.…”

Oxidative C–C/C–X coupling in organometallic nickel complexes: insights from DFT

“…5 They possess significant reactivity similarities; nickel catalysts are preferred over palladium catalysts, however, to save costs and reduce toxicity problems. Nickel is more liable for oxidative addition [6][7][8][9] compared with palladium and this reduces to a greater extent the common problem encountered in palladium catalysis such as b-hydride elimination and palladium black deposition. 10 The major advantage is that nickel can exist in more oxidation states that are easily accessible compared with palladium.…”

“…Recent reports have indicated that, among the various oxidation states of nickel, such as Ni 0-IV , Ni IV is one of the crucial reactive intermediates in the catalytic cycle. 7,8,11,12 The development of Ni-based catalysis over the past several decades has led to the ability to perform cross-coupling reactions with Ni catalysts, 13 which has played a significant role in the development of numerous pharmaceuticals, fine chemicals, natural products and polymers. 14,15 Earlier reports have shown that Ni catalytic reactions typically employ a catalytic cycle that involves Ni 0 /Ni II .…”