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

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.