HX ELIMINATION FROM IR(H)(2)X(PBU(T)(2)PH)(2) PROMOTED BY CO COORDINATION - ASSESSMENT OF X LIGAND INFLUENCE

The coordinatively unsaturated complexes Ir(H)(2)X((PBu2Ph)-Ph-t)(2) [ X = Cl, Br, I, N-3, N=C=NSiMe3, NHC(O)CH3, OC(O)CF3, OSO2CF3, OC(O)CH3 , SPh OPh, F] all react within the mixing time in arene solvents to bi nd carbon monoxide. Subsequent reactivity of these CO adducts reductiv ely to eliminate HX is dependent on the magnitude of the inherent dest abilization caused by filled-filled repulsions between the ligand p(pi ), orbitals and metal d(pi), orbitals. This destabilization is not suf ficient to promote the loss of HX when X = Cl, Br, I, N,, N=C=NSiMe,, NHC(O)CH, or OC(O)CF,. When X = OC(O)CH, or SPh, metastable CO adducts are formed that ultimately lose HX. The complexes containing OPh or F quickly lose HX upon reaction with CO. The unusual iridium(I) complex es IrH(CO)(2)((PBu2Ph)-Ph-t) and IrH(CO)((PBu2Ph)-Ph-t)(2) have been c haracterized by multinuclear NMR and IR spectroscopy. The reaction of Ir(H),(F)(PBu:Ph), with CO in a glass vessel yields crystalline [Ir(H) (2)(CO)(2)((PBu2Ph)-Ph-t)(2)][SiF5] and [Ir(CO)(2)((PBu2Ph)-Ph-t)(2)][ SiF5]. C6D6, both characterized by X-ray diffraction. The latter, alth ough approximately square planar, has a C-Ir-C angle of only 162.7 deg rees. Crystallographic data (Pe at -165 degrees C) for [Ir(H)(2)(CO)(2 )((PBu2Ph)-Ph-t)(2)][SiF5], a = 8.293(2), b = 12.462(5), c = 16.333(7) A, B = 98.21(2)degrees with Z = 2. Crystallographic data (P2(1)/n at -172 degrees C) for[Ir(CO)(2)((PBu2Ph)-Ph-t)(2)][SiF5]. C6D6, a = 13.0 41(7), b = 12.998(5), c = 22.553(13) Angstrom, beta 97.50(2)degrees wi th Z = 4.