PHOTOCHEMICAL GENERATION OF 16-ELECTRON [RH(ETA(5)-C5H5)-(PME(3))] AND [IR(ETA(5)-C5H5)(PME(3))] IN LOW-TEMPERATURE MATRICES - EVIDENCE FOR METHANE ACTIVATION

The photochemical reactions of [Rh(eta(5)-C5H5)(PMe(3))(H)(2)] and [Ir(eta(5)-C5H5)(PMe(3))(H)(2)] have been studied in Ar, CH4, N-2 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(eta(5)-C5H5)(PMe(3))] with characteristic visible absorption maxima (M = Rh, lambda(max) 399 and 488 nm; M = Ir, lambda(max) 436 and 526 nm). The reaction is partially reversed by long-wavelength photolysis. The conversion of [Rh(eta(5)-C5H5)(PMe(3))(H)(2)] to [Rh(eta(5)-C5H5)(PMe(3))(Me)H] on photolysis in methane matrices is confirmed by extensive isotopic labelling studies and by the use of alternative precursors for the methyl hydride, viz. [Rh(eta(5)-C5H5)(PMe(3))(eta(2)-C6F6)] and [Rh(eta(5)-C5H5)(PMe(3))(C2H4)]. Evidence has also been obtained to show that irradiation of [Ir(eta(5)-C5H5)(PMe(3))(H)(2)] in methane yields [Ir(eta(5)-C5H5)(PMe(3))(Me)H]. Photolysis of [M(eta(5)-C5H)(PMe(3))(H)2] in N-2 and CO-doped Ar matrices generates [M(eta(5)-C5H5)(PMe(3))L] (M = Rh or Ir, L = N-2 or CO).