Science, Vol.278, No.5336, 260-263, 1997
The Mechanism of a C-H Bond Activation Reaction in Room-Temperature Alkane Solution
Chemical reactions that break alkane carbon-hydrogen (C-H) bonds are normally carried out under conditions of high temperature and pressure because these bonds are extremely strong (similar to 100 kilocalories per mole), but certain metal complexes can activate C-H bonds in alkane solution under the mild conditions of room temperature and pressure. Time-resolved infrared experiments probing the initial femtosecond dynamics through the nano-and microsecond kinetics to the final stable products have been used to generate a detailed picture of the C-H activation reaction. Structures of all of the intermediates involved in the reaction of Tp*Rh(CO)(2) (Tp* = HB-Pz(3)*, Pz* = 3,5-dimethylpyrazolyl) in alkane solution have been identified and assigned, and energy barriers for each reaction step from solvation to formation of the final alkyl hydride product have been estimated from transient lifetimes.
Keywords:FEMTOSECOND TRANSIENT ABSORPTION;RESOLVED INFRARED-SPECTROSCOPY;(HBPZ’(3))RH(CO)(2) PZ’=3;5-DIMETHYLPYRAZOLYL;SOLUTION PHOTOCHEMISTRY;OXIDATIVE ADDITION;VIBRATIONAL-ENERGY;METAL-COMPLEXES;ULTRAFAST;MATRIX;DYNAMICS