PHOTOOXIDATION OF MATRIX-ISOLATED NICKEL TETRACARBONYL IN THE PRESENCE OF DIOXYGEN

UV Photolysis (lambda = ca. 254 nm) of Ni(CO)(4) molecules isolated in O-2-doped argon matrices at ca. 20 K has been monitored by reference to the IR spectra of the matrices. These spectra indicate that Ni(CO)( 4) undergoes photooxidation to give four distinct nickel carbonyl inte rmediates A-D with the release of CO and CO2, ultimately to arrive at the final product (eta(2)-O-2)(2)Ni. The stoichiometry and likely stru cture of each intermediate A-D have been deduced by analysis of the nu mber, energies, and relative intensities of its IR absorptions, with p articular reference to the response to (CO)-C-13- and O-18-enrichment. Hence, the following identities have been inferred: A, Ni(CO)(3); B, (eta(2)-O2)Ni(CO)(2); C, (O-2)Ni(CO)(3); and D, O=Ni(CO)(2). The syste m exhibits some photoselectivity, and reversal of the reactions leadin g to A-D can be effected under the action of UV radiation with wavelen gths near 313 nm or by annealing the deposit to ca. 30-35 K. A partial mechanism is proposed to account for the course of the matrix reactio ns.