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

Abstract

After the successful creation of the newly designed PCP carbodiphosphorane (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 interest. Two different iridium complexes, namely (bis{[(diphenylphosphanyl)methyl]diphenylphosphanylidene}methane-κ3P,C,P′)carbonylchloridohydridoiridium(III) chloride dichloromethane trisolvate, [IrIII(CO){C(dppm)2-κ3P,C,P′}ClH]Cl·3CH2Cl2 (1) and the closely related (bis{[(diphenylphosphanyl)methyl]diphenylphosphanylidene}methanide(1+)-κ3P,C,P′)carbonylchloridohydridoiridium(III) dichloride–hydrochloric acid–water (1/2/5.5), [IrIII(CO){CH(dppm)2-κ3P,C,P′)ClH]Cl}2 (2), have been designed and both complexes show a slightly distorted octahedral 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 P2C2 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 carbodiphosphorane carbon atom located antiperiplanar 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 carbodiphosphorane carbon atom.

Keywords

• iridium (III)
• PCP pincer
• carbodiphosphorane (CDP)
• crystal structure
• NMR