Time-resolved infrared study of reactive species produced by flash photolysis of the hydroformylation catalyst precursor Co2(CO)6(PMePh2)2

Flash photolysis with time-resolved infrared (TRIR) spectroscopy was used to elucidate the photochemical reactivity of the hydroformylation catalyst precursor Co2(CO)6(PMePh2)2. Depending on reaction conditions, the net products of photolysis varied significantly. A model is presented that accounts for the net reactivity with two initial photoproducts, the 17-electron species Co(CO)3(PMePh2) and the coordinatively unsaturated dimer Co2(CO)5(PMePh2)2. No evidence was found for photochemical formation of Co2(CO)6(PMePh2). Time-resolved spectroscopic studies allowed for the direct observation of transient species and for kinetics studies of certain reactions; for example, the reactions of Co(CO)3PMePh2 with CO and with PMePh2 gave the respective rate constants 1.5 × 105 and 1.2 × 107 M−1 s−1, while the analogous reactions with Co2(CO)5(PMePh2)2 gave the rate constants of 2.6 × 106 M−1 s−1 and 3.9 × 107 M−1 s−1.