Crystal structures of the [Ir III {C(C 4 H 6 O 2 )(dppm)-κ 3 P , C , O }(dppm)H](CF 3 O 3 S) 2 and [Ir III {C(C 4 H 6 O 2 )(dppm)-κ 2 P , C }(CO)(dppm)H](CF 3 O 3 S) 2 phosphorus ylide complexes, generated by a Wittig-type carbon-carbon coupling reaction of a carbodiphospho-rane PCP ligand system.

The reaction of [IrIII {C(dppm)2 -κ3 P , C , P '}ClH(NH3 C2 )]Cl with ethyl diazo-acetate, a well known C=C coupling reagent, leads to the formation of a C=C unit, accompanied by N2 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 facial manner. The phospho-rus electron-donor atoms and the ylide carbon atom of the resulting [IrIII {C(C4 H6 O2 )(dppm)-κ3 P , C , O }(dppm)H](CF3 O3 S)2 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-κ3 P , C , O )hydridoiridium(III) bis-(tri-fluoro-methane-sulfonate), 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-(di-phenyl-phosphan-yl)methane]-carbon-yl({[(di-phenyl-phosphan-yl)meth-yl]di-phenyl-phosphanyl-idene}(eth-oxy-oxoethanyl-idene)methanyl-idene-κ2 P , C }hydridoiridium(III) bis-(tri-fluoro-methane-sulfonate)-di-chloro-methane-ethyl acetate (6/2/3) or, more simply, [IrIII {C(C4 H6 O2 )(dppm)-κ2 P , C }(CO)(dppm)H](CF3 O3 S)2 ·0.33CH2 Cl2 ·0.5C4 H8 O2 . One tri-fluoro-meth-ane-sulfonate counter-ion of 3 shows positional disorder in a 2:1 ratio. Complex 4 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.