CAGE EFFECTS IN ORGANOMETALLIC RADICAL CHEMISTRY - FRACTIONAL CAGE-RECOMBINATION EFFICIENCY FOR PHOTOCHEMICAL CAGED-PAIR INTERMEDIATES OF CP'2M2(CO)6 (M = MO AND W CP' = ETA-5-C5H4CH3)

A new method is reported for measuring photochemical cage-efficiency factors, F(cP), in photochemically generated radical cage pairs. (The photochemical r-age-efficiency factor is defined as k(cP)/(k(cP) + k(dP)), where k(cP) is the rate constant for cage recombination of a photochemically generated radical cage pair and k(dP) is the rate constant for cage escape.) The method was applied to the measurement of F(cP) values for [Cp'(CO)3M..M(CO)3Cp'] caged pairs (M = Mo, W) in solvent systems of various viscosities. The results show that there is a significant cage effect even in common solvents. For example, F(cP) is predicted to be congruent-to 0.3 for the [CP'(CO)3Mo..Mo(CO)3Cp'] caged pair in cyclohexane at 23-degrees-C.