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 Co-2(CO)(8). There appears to be minimal interaction between CO(CO)4 and the solvent, but significant solvation of 'Co-2(CO)(7)'. The Co-2(CO)(7):Co(CO)(4) ratio depends very strongly on the photolysis wavelength: photolysis in n-heptane at 266 nm or 308 nm produces [Co-2(CO)(7)] and [CO(CO)(4)] in a ratio of similar to 2:1, but the ratio following 355 nm photolysis is similar to 1:4. The wavelength dependence of the branching ratio is discussed in terms of the electronic spectrum of Co-2(CO)(8). (c) 2006 Elsevier B.V. All rights reserved.