Photochemical formation of a metal-metal bond following outer-sphere intervalence excitation in the ion pair [CoI(CO)3(PPh3)2][Co -I(CO)4]

Article abstract of DOI:10.1021/om00096a036

The absorption spectrum of the ion pair [Co^I(CO)₃(PPh₃)₂][Co ^-I(CO)₄] in acetone displays a long-wavelength band at λ_max = 386 nm that is assigned to an intervalence transfer (IT) transition from Co^-I to Co^+I. Upon IT excitation a photoreaction occurs according to the equation [Co^I(CO)₃(PPh₃)₂][Co ^-I(CO)₄] → [(PPh₃)-(CO)₃Co⁰-Co⁰(CO) ₃PPh₃] + CO with a quantum yield of Φ = 0.012. It is suggested that in the primary photochemical step the radicals [Co(CO)₃(PPh₃)₂] and [Co(CO)₄] are generated. These radicals are labile and undergo dissociation and substitution reactions and finally dimerize to yield the stable photoproduct.