Reaction mechanism of silicon-hydrogen bond activation studied using femtosecond to nanosecond IR spectroscopy and Ab initio methods

Photolysis of CpMn(CO)₃ in neat Et₃SiH at ambient temperatures results in the initial generation of CpMn(CO)₂ in two spin states, with differing geometries, selectivities, and rates of reaction. While the apparent rate- determining step for the activation of triethylsilane for singlet CpMn(CO)₂ and CpRe(CO)₂ is the dissociative rearrangement of the ethyl-bound solvate, triplet CpMn(CO)₂ interacts only weakly with the solvent C-H bonds, allowing facile reorientation of Et₃SiH until the strongly coupling Si-H bond is encountered. The identities of transient species detected by ultrafast infrared spectroscopy were assigned with the aid of ab initio theoretical methods.