Abstract The thermal decomposition of arylmethylbis (triethylphosphine) nickel (II), ArNiMeL 2, is studied in hydrocarbon solutions, both in the presence and absence of aryl halide. The direct thermolysis affords methylarenes without aryl scrambling, by first-order kinetics. The inverse phosphine dependence of the rate is related to a dissociative mechanism proceeding via reductive elimination directly from the coordinatively unsaturated ArNiMeL ...