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

Abstract

Flash photolysis with time-resolved infrared (TRIR) spectroscopy was used to elucidate the photochemical reactivity of the hydroformylation catalyst precursor Co 2(CO) 6(PMePh 2) 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(PMePh 2) and the coordinatively unsaturated dimer Co 2(CO) 5(PMePh 2) 2. No evidence was found for photochemical formation of Co 2(CO) 6(PMePh 2). 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) 3PMePh 2 with CO and with PMePh 2 gave the respective rate constants 1.5 × 10 5 and 1.2 × 10 7 M −1 s −1, while the analogous reactions with Co 2(CO) 5(PMePh 2) 2 gave the rate constants of 2.6 × 10 6 M −1 s −1 and 3.9 × 10 7 M −1 s −1.