Photochemical generation of 16-electron [Rh(η5)-C5H5)-(PMe3)] and [Ir(η5-C5H5)(PMe3)] in low-temperature matrices: evidence for methane activation
Abstract
The photochemical reactions of [Rh(η5-C5H5)(PMe3)(H)2] and [Ir(η5-C5H5)(PMe3)(H)2] have been studied in Ar, CH4, N2 and CO-doped argon matrices by IR and UV/VIS spectroscopy. The UV photolysis in argon matrices results in the formation of the 16-electron complexes [M(η5-C5H5)(PMe3)] with characteristic visible absorption maxima (M = Rh, λmax 399 and 488 nm; M = Ir, λmax, 436 and 526 nm). The reaction is partially reversed by long-wavelength photolysis. The conversion of [Rh(η5-C5H5)(PMe3)(H)2] to [Rh(η5-C5H5)(PMe3)(Me)H] on photolysis in methane matrices is confirmed by extensive isotopie labelling studies and by the use of alternative precursors for the methyl hydride, viz.[Rh(η5-C5H5)(PMe3)(η2-C6F6)] and [Rh(η5-C5H5)(PMe3)(C2H4)], Evidence has also been obtained to show that irradiation of [Ir(η5-C5H5)(PMe3)(H)2] in methane yields [Ir(η5-C5H5)(PMe3)(Me)H]. Photolysis of [M(η5-C5H5)(PMe3)(H)2]in N2 and CO-doped Ar matrices generates [M(η5-C5H5)-(PMe3)L](M = Rh or Ir, L = N2 or CO).