Crystal structures of the [IrIII{C(C4H6O2)(dppm)-κ3P,C,O}(dppm)H](CF3O3S)2 and [IrIII{C(C4H6O2)(dppm)-κ2P,C}(CO)(dppm)H](CF3O3S)2 phosphorus ylide complexes, generated by a Wittig-type carbon-carbon coupling reaction of a carbodiphosphorane PCP ligand system

The reaction of [Ir-III{C(dppm)(2)-kappa P-3,C,P'}ClH(NH3C2)]Cl with ethyl diazoacetate, a well known C=C coupling reagent, leads to the formation of a C=C unit, accompanied by N-2 abstraction, reorganization of a dppm subunit and, considered as a whole, to the transformation of the PCP pincer carbodiphosphorane system to a phosphorus ylide ligand. After removal of the halogenides, the iridium center is stabilized by the carbonyl O atom through the formation of a five-membered chelate ring. A PCO pincer ligand system is thereby generated, which coordinates the iridium(III) atom threefold in a facial manner. The phosphorus electron-donor atoms and the ylide carbon atom of the resulting [Ir-III{C(C4H6O2)(dppm)-kappa P-3,C,O}(dppm)H](CF3O3S)(2) complex, also termed as [bis(diphenylphosphanyl)methane]({[(diphenylphosphanyl)methyl]diphenylphosphanylidene}(ethoxyoxoethanylidene)methanylidene-kappa P-3,C,O)hydridoiridium(III) bis(trifluoromethanesulfonate), are in plane and the hydrido ligand and the carbonyl O atom are located trans to each other, perpendicular to the meridional plane. The addition of carbon monoxide causes a replacement of the carbonyl O atom of the acetate subunit by a carbonyl ligand, thereby creating [bis(diphenylphosphanyl)methane]carbonyl({[(diphenylphosphanyl)methyl]diphenylphosphanylidene}(ethoxyoxoethanylidene)methanylidene-kappa P-2,C}hydridoiridium(III) bis(trifluoromethanesulfonate)-dichloromethane-ethyl acetate (6/2/3) or, more simply, [Ir-III{C(C4H6O2)(dppm)kappa P-2,C}(CO)(dppm)H](CF3O3S)(2)center dot 0.33CH(2)Cl(2)center dot 0.5C(4)H(8)O(2). One trifluoromethanesulfonate counter-ion of 3 shows positional disorder in a 2:1 ratio. Complex 4 shows pseudo-merohedral twinning (matrix: (1) over bar 0 0 0 (1) over bar 0 1 0 1). The dichloromethane solvent is disordered over two orientations with occupation factors of 0.5 and 0.166.