Novel PC II P-Ir I monochloride complexes (1-Cl and 2-Cl) bearing a phosphine-carbene-phosphine pincer type ligand were synthesized. Reactions of 1-Cl with hexachloroethane, hydrogen chloride, and lithium triethylborohydride under a dihydrogen atmosphere afforded PC II P-Ir III trichloride (1-Cl 3 ), hydride dichloride (1-HCl 2 ), and trihydride (1-H 3 ) complexes, respectively. The strong electron-donating ability of carbene in PC II P-Ir complexes was confirmed by X-ray crystallography and DFT calculations. Moreover, in complex 1-Cl, strong π backdonation from the iridium center to the carbene carbon was observed. Hydrogenation of CO 2 with triethanolamine catalyzed by PC II P-Ir complexes was investigated. The novel PC II P-Ir complex 1-Cl exhibited a longer lifetime in comparison to the PNP-Ir III complex 3-H 3 : the turnover number of 1-Cl is significantly higher than that of 3-H 3 (in 46 h, 1-Cl 230000 and 3-H 3 54000).

PC(sp3)P-Ir complexes bearing two geminal boron atoms attached to the central carbon anion were synthesized. Strong σ-donation and unique back-donation to the boron atom at the β-position were observed.

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