Flash Infrared Kinetics of the Photochemistry of Tp*Rh(CO)2 and Bp*Rh(CO)2 in Liquid Xenon Solution

Abstract

The photochemistry of Tp*Rh(CO)2 (1; Tp* = hydridotris(3,5-dimethylpyrazolyl)borate) in liquid xenon solution at −50 °C has been examined by flash IR kinetic spectroscopy. IR spectra of the solution taken 2 μs after 308 nm photolysis exhibit two transient bands at 1976−1980 and 1994−1998 cm-1, respectively, both of which decay with the same first-order rate constant (k = 2 × 104 s-1). In the presence of excess CO, the rates of decay of both of these bands increase by an order of magnitude and correlate with the rate of recovery of the CO stretch of the parent complex. Photolysis of xenon solutions of Bp*Rh(CO)2 (5; Bp* = dihydridobis(3,5-dimethylpyrazolyl)borate) produces a transient species with a single IR absorption at 1996−2000 cm-1. Upon addition of pyridine to the solution, this transient photoproduct reacts to form the new, stable complex Bp*Rh(CO)(pyridine), with an IR absorption at 1978 cm-1. On the basis of these results, the 1978 and 1996 cm-1 bands observed upon photolysis of 1 are attributed ...