PHOTOOXIDATION OF [V(CO)6] IN LOW-TEMPERATURE MATRICES CONTAINING O2 - FORMATION OF A NOVEL SUPEROXOVANADIUM SPECIES

Irradiation of [V(CO)6] in low-temperature matrices containing O2 led to the formation of a novel superoxovanadium species A alongside free CO2. Isotopic substitution experiments involving O-18 and comparison of the IR spectrum of A with that of the known oxovanadium species [VO2Cl2]- and [VO2F2]- indicate that A is the superoxide [VO2(sigma-O2)]. The O-16-O-18 isotopic shift for V(asym)(VO2) of A gives an upper limit of ca. 115-degrees for the OVO bond angle of the dioxo moiety of A; the intensity ratio of the bands arising from v(sym) and v(asym)(VO2) suggests a value of 108 +/- 5-degrees for this angle. The reaction is initiated by loss of CO from [V(CO)6] to form [V(CO)5]; a step which is shown to be photochromic, and proceeds via at least one oxocarbonyl intermediate.