SOLVENT-INITIATED PHOTOCHEMISTRY OF TRANSITION-METAL COMPLEXES

Although it is generally assumed that photoreactions of transition met al complexes proceed through metal complex excited states, some reacti ons in halogenated solvents occur instead as radical processes, follow ing carbon-halogen bond homolysis. Oxidation, substitution, or oxidati ve addition can occur by either a metal-centered or a solvent-initiate d photoreaction, and they can be hard to distinguish. Under some circu mstances even the kinetic rate laws can be the same. However, with pro per choice of irradiation wavelength the dependence of the initial rat e on light intensity and metal complex concentration suffices to discr iminate between the two possibilities. (C) 1997 Elsevier Science S.A.