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.