Microsecond UV flash photolysis of Co2(CO)8 in solution: Wavelength dependence of the Co(CO)4/Co2(CO)7 branching ratio

Time-resolved step-scan Fourier transform infrared spectroscopy is used to observe, for the first time in room-temperature solution, the coordinatively unsaturated species Co(CO)4 and Co2(CO)7, the products of UV flash photolysis of Co2(CO)8. There appears to be minimal interaction between Co(CO)4 and the solvent, but significant solvation of ‘Co2(CO)7’. The Co2(CO)7:Co(CO)4 ratio depends very strongly on the photolysis wavelength: photolysis in n-heptane at 266 nm or 308 nm produces [Co2(CO)7] and [Co(CO)4] in a ratio of ∼2:1, but the ratio following 355 nm photolysis is ∼1:4. The wavelength dependence of the branching ratio is discussed in terms of the electronic spectrum of Co2(CO)8.