Oxidative addition of aryl halides to tris(triphenylphosphine)nickel(0)

The oxidative addition of aryl halides, RC6H4X, to tris(triphenylphosphine)nickel(0) has been studied (R = H, m- or p-Me, -Cl, -CN, and -OPh, p-OMe, -COMe, and -COPh, and m-CO2Me; X = Cl, Br, or I). The effects of substituents on the aryl halides and of the halide as leaving group have been investigated by competitive measurements. The reactions of p-chloroanisole and p- and m-dichlorobenzene display first-order kinetics with respect to the aryl halides and the nickel complex. Triphenylphosphine decreases the reaction rate. The mechanistic implications of these results are discussed.