Picosecond photochemistry of Cr(CO)6: Solvation and dynamics of the primary intermediate

Picosecond absorption spectroscopy has been used to examine the primary photoproduct of Cr(CO)₆ in both neat and mixtures of THF and cyclohexane. The primary intermediate observed is shown to be the solvated pentacarbonyl in which one solvent molecule occupies the coordination site created by the photoelimination of CO. The rate of exchange of cyclohexane from (cyclohexane)Cr(CO)₅ by THF to form (THF)Cr(CO)₅ was found to be bimolecular, k = (4 ± 1) × 10⁷ mole^?1 s^?1, with an enthalpy and entropy of activation of 1 ± 1 kcal/mole and ?20 ± 4 eu, respectively.