Absolute rate constants for the coordination of olefins to a transient coordinatively unsaturated cobalt complex

Absolute second-order rate constants for the coordination of diethyl phenylphosphonite and various olefins to a transient coordinatively unsaturated cobalt complex, i.e. hydridotris(diethyl phenylphosphonite)cobalt(I), have been measured in cyclohexane at 23° C using laser flash photolysis techniques. The rate constants have been found to depend markedly on the structures of the olefins, e.g. 1.2 × 10⁸ and 6.5 × 10⁴M^?1 s^?1 for 1-hexene and tetramethylethylene, respectively. The mechanism of photochemical double-bond migration catalyzed by the transient is discussed on the basis of these rate constants.