Triplet organometallic reactivity under ambient conditions: An ultrafast UV pump/IR probe study

: The reactivity of triplet 16-electron organometallic species has been stu died in room-temperature solution using femtosecond UV pump IR probe spectr oscopy. Specifically, the Si-H bond-activation reaction of photogenerated t riplet Fe(CO)(4) and triplet CpCo(CO) with triethylsilane has been characte rized and compared to the known singlet species CpRh(CO). The intermediates observed were studied using density functional theory (DFT) as well as ab initio quantum chemical calculations. The triplet organometallics have a gr eater overall reactivity than singlet species due to a change in the Si-H a ctivation mechanism, which is due to the fact that triplet intermediates co ordinate weakly at best with the ethyl groups of triethylsilane. Consequent ly, the triplet species do not become trapped in alkyl-solvated intermediat e states. The experimental results are compared to the theoretical calculat ions, which qualitatively reproduce the trends in the data.