Crystal structure of an iridium(III) complex of the [C(dppm) 2 ] PCP pincer ligand system and its conjugate CH acid form.

After the successful creation of the newly designed PCP carbodi-phospho-rane (CDP) ligand [Reitsamer et al. (2012 ▸). Dalton Trans. 41 , 3503-3514; Stallinger et al. (2007 ▸). Chem. Commun. pp. 510-512], the treatment of this PCP pincer system with the transition metal iridium and further the analysis of the structures by single-crystal diffraction and by NMR spectroscopy were of major inter-est. Two different iridium complexes, namely (bis-{[(di-phenyl-phosphan-yl)meth-yl]di-phenyl-phosphanyl-idene}methane-κ3 P , C , P ')carbonyl-chlorido-hydridoiridium(III) chloride di-chloro-methane tris-olvate, [IrIII (CO){C(dppm)2 -κ3 P , C , P '}ClH]Cl·3CH2 Cl2 ( 1 ) and the closely related (bis-{[(di-phenyl-phosphan-yl)meth-yl]di-phenyl-phosphanyl-idene}methanide(1+)-κ3 P , C , P ')carbonyl-chlorido-hy-dridoirid-ium(III) dichloride-hydro-chloric acid-water (1/2/5.5), [IrIII (CO){CH(dppm)2 -κ3 P , C , P ')ClH]Cl}2 ( 2 ), have been designed and both complexes show a slightly distorted octa-hedral coordinated IrIII centre. The PCP pincer ligand system is arranged in a meridional manner, the CO ligand is located trans to the central PCP carbon and a hydride and chloride are located perpendicular above and below the P2 C2 plane. With an Ir-CCDP distance of 2.157 (5) Å, an Ir-CO distance of 1.891 (6) Å and a quite short C-O distance of 1.117 (7) Å, complex 1 presents a strong carbonyl bond. Complex 2 , the corresponding CH acid of 1 , shows an additionally attached proton at the carbodi-phospho-rane carbon atom located anti-periplanar to the hydride of the metal centre. In comparison with complex 1 , the Ir-CCDP distance of 2.207 (3) Å is lengthened and the Ir-C-O values indicate a weaker trans influence of the central carbodi-phospho-rane carbon atom.