Crystal structures of the [Ir{C(CHO)(dppm)-κ ,,}(dppm)H](CFOS) and [Ir{C(CHO)(dppm)-κ ,}(CO)(dppm)H](CFOS) phosphorus ylide complexes, generated by a Wittig-type carbon-carbon coupling reaction of a carbodiphospho-rane PCP ligand system.

The reaction of [Ir{C(dppm)-κ ,,'}ClH(NHC)]Cl with ethyl diazo-acetate, a well known C=C coupling reagent, leads to the formation of a C=C unit, accompanied by N abstraction, reorganization of a dppm subunit and, considered as a whole, to the transformation of the PCP pincer carbodi-phospho-rane system to a phospho-rus 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 manner. The phospho-rus electron-donor atoms and the ylide carbon atom of the resulting [Ir{C(CHO)(dppm)-κ ,,}(dppm)H](CFOS) complex, also termed as [bis-(di-phenyl-phosphan-yl)methane]({[(di-phenyl-phosphan-yl)meth-yl]di-phenyl-phosphanyl-idene}(eth-oxy-oxoethanyl-idene)methanyl-idene-κ ,,)hydridoiridium(III) bis-(tri-fluoro-methane-sulfonate), are in plane and the hydrido ligand and the carbonyl O atom are located to each other, perpendicular to the 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-(di-phenyl-phosphan-yl)methane]-carbon-yl({[(di-phenyl-phosphan-yl)meth-yl]di-phenyl-phosphanyl-idene}(eth-oxy-oxoethanyl-idene)methanyl-idene-κ ,}hydridoiridium(III) bis-(tri-fluoro-methane-sulfonate)-di-chloro-methane-ethyl acetate (6/2/3) or, more simply, [Ir{C(CHO)(dppm)-κ ,}(CO)(dppm)H](CFOS)·0.33CHCl·0.5CHO. One tri-fluoro-meth-ane-sulfonate counter-ion of shows positional disorder in a 2:1 ratio. Complex shows pseudo-merohedral twinning (matrix: 0 0 0 0 1 0 1). The di-chloro-methane solvent is disordered over two orientations with occupation factors of 0.5 and 0.166.