Photodissociation of chromium hexacarbonyl in solution: direct observation of the formation of pentacarbonyl(methanol)chromium

Abstract

Time-resolved picosecond absorption spectroscopy has been used to examine the dynamics of formation of Cr(CO)/sub 5/(solvent) generated by photolysis of Cr(CO)/sub 6/ in methanol and cyclohexane solutions. The kinetics were monitored at the absorption maximum of Cr(CO)/sub 5/S, 460 +/- 5 and 500 +/- 5 nm for methanol and cyclohexane, respectively. In methanol, a rise time of 2.5 ps is observed. This is compared to the instrument response of 0.8 ps, measured by determining the rise of the S/sub 1/ ..-->.. S/sub N/ absorption of trans-stilbene. In cyclohexane, the transient is found to rise within the time resolution of the experiment. The longer rise observed in methanol is discussed in terms of the solvent restructuring leading to the formation of the Cr-S bond.