The identification of the intermediates observed in bond activation reactions involving
organometallic complexes on time scales from femtoseconds to milliseconds has been
accomplished through the use of ultrafast infrared spectroscopy. C—H bond activation
by the molecule Tp*Rh(CO)2 showed a final activation time of 200 ns in cyclic solvents,
indicating a reaction barrier of 8.3 kcal/mol. An important intermediate is the partially
dechelated η2-Tp*Rh(CO)(S) solvent complex, which was formed 200 ps after the initial
photoexcitation. Si—H bond activation by CpM(CO)3 (M=Mn, Re) showed some
product formation in less than 5 ps, indicating that the Si—H activation reaction is
barrierless. The activated product was formed on several timescales, from picoseconds to
nanoseconds, suggesting that there are different pathways for forming final product
which are partitioned by the initial photoexcitation.
Rh-catalyzed decarbonylation of conjugated ynones via carbon–alkyne bond activation: reaction scope and mechanistic exploration via DFT calculations
