Hydrosilation catalysis via silylmanganese carbonyl complexes: thermal vs. photochemical activation

Thermal and photochemical activation of Ph3SiMn(CO)5 leads to different catalyst systems, both of which promote the addition of organosilicon hydrides to terminal alkenes. In the thermal case, major catalytic activity is due to triphenylsilyl radicals generated from SiMn bond homolysis. Upon photolysis, however, there is no evidence of SiMn homolysis during catalyst activation. These studies represent the first well-defined example of disparate behavior upon photochemical vs. thermal activation of the same catalyst precursor.