Oxidative Addition of Aryl Halides to a Triphosphine Ni(0) Center to Form Pentacoordinate Ni(II) Aryl Species

Abstract

Oxidative addition of aryl halides to Ni(0) is a ubiquitous elementary step in cross-coupling and related reactions, usually producing a square-planar Ni­(II)–aryl intermediate. Here we show that a triphosphine ligand supports oxidative addition at a tris-ligated Ni(0) center to cleanly form stable five-coordinate Ni­(II)–aryl compounds. Kinetic and computational studies support a concerted, two-electron mechanism rather than radical halogen abstraction. These results support the idea that oxidative addition to triphosphine Ni(0) species may be more generally involved in Ni/phosphine catalytic systems.

Reactions of nickel(0) with organochlorides, organobromides, and organoiodides: mechanisms and structure/reactivity relationships

“…Pérez-García et al have studied the reactions of nickel(0) complexes with a tris(phosphine) ligand (Scheme 9). 56 The treatment of the nickel(0) complex with haloarenes led to the formation of well-defined nickel(II) oxidative addition products, of which one example was structurally characterised by X-ray diffraction analysis.…”

Bis-ferrocenyl-hydrazide metal complexes: studying electronic functional groups as newly potent homogeneous photocatalysts for C(sp3)–H and C(sp2)–H bond oxidation utilizing visible light condition

“…Thus, the homogeneous dispersion and distinct electronic activity of bis-ferrocene scaffolds in metal complexes result in the in situ generation of reactive oxygen species and the benzylic cation. 102,103 Finally, intermediate II leads to the formation of an oxygenated compound (benzaldehyde). 104 For the styrene oxidation reaction, the most probable mechanism is shown in Fig.…”

Mechanistic Studies of the Oxidative Addition of Aryl Halides to Ni(0) Centers Bearing Phosphine Ligands

“…Using this hypothesis as a starting point, we recently reported a combined experimental and computational mechanistic study of the oxidative addition of aryl halides to a Ni(0) center bearing the tridentate ligand PPP p-tol (PPP p-tol = bis(2-bis(p-tolyl) phosphinophenyl)-phenylphosphine). [21] The reaction between (PPP p-tol )Ni 0 (BPI) (BPI = benzophenone imine, a labile coligand) and aryl halides cleanly produced stable pentacoordinated (PPP p-tol )Ni II (Ar)X complexes (Scheme 5). The X-ray crystal structure analysis showed a trigonal bipyramidal structure with a facial coordination for the tridentate ligand, an axial aryl ligand and an equatorial halide ligand.…”