Carbon–Carbon Bond-Forming Reductive Elimination from Isolated Nickel(III) Complexes

Abstract

This manuscript describes the design, synthesis, characterization, and reactivity studies of organometallic Ni complexes of general structure TpNi(R)(R) (Tp = tris(pyrazolyl)borate). With appropriate selection of the R and R ligands, the complexes are stable at room temperature and can be characterized by cyclic voltammetry, EPR spectroscopy, and X-ray crystallography. Upon heating, many of these Ni compounds undergo C(sp)-C(sp) or C(sp)-C(sp) bond-forming reactions that are challenging at lower oxidation states of nickel.

A catalytic fluoride-rebound mechanism for C(sp 3 )-CF 3 bond formation

“…Such a low barrier likely explains why competitive hydrolysis of the difluorocarbene, common in metal halocarbene complexes, was not observed here even in wet solvent (28). Regardless, this mechanism is unusual because it represents a formal C(sp 3 )-CF 3 reductive elimination—itself rarely if ever observed—by a catalytic process involving iterative disassembly and reassembly of the CF 3 moiety (29–31). …”

C−H Bond Trifluoromethylation of Arenes Enabled by a Robust, High‐Valent Nickel(IV) Complex

“…[8] In fact, reductive elimination of Ar À CF 3 from well-defined ArNi II CF 3 species has been shown to be unfeasible by the groups of Vicic [9a] and Grushin. [12] Since 2015, the first Ni IV CF 3 organometallics (I-IV;S cheme 1a)h ave been synthesized by Sanford and co-workers, [13] with scorpionate-type ligands to stabilize the high-valent Ni IV center. [12] Since 2015, the first Ni IV CF 3 organometallics (I-IV;S cheme 1a)h ave been synthesized by Sanford and co-workers, [13] with scorpionate-type ligands to stabilize the high-valent Ni IV center.…”

Nickel-Catalyzed Inter- and Intramolecular Carbon-Sulfur Bond Metathesis by Reversible Arylation

“…Single-crystal X-ray analysis confirmed the identity of the oxidative addition product 5 (Scheme 2A). Gratifyingly,t he 31 P{H} NMR resonances matched the resonances of the previously observed compound, (Scheme 2B), thus confirming the viability of the transmetallation step.T he identity of complex 6 was further confirmed by X-ray analysis.W hile reductive elimination from Ni III has often been reported, [24,25] such apathway is not viable under our catalytic conditions because of the microscopic reversibility principle.Reductive elimination from Ni II complex 6 provides am ore reasonable pathway to close the catalytic cycle (Scheme 2C). Ther eaction was very slow at room temperature,h owever,i ncreasing the temperature to 90 8 8Cr esulted in the formation of an ew set of doublets (d = 62), reaching up to 30 %c onversion overnight ( Figure S5).…”