Alkene and alkyne insertion into the Ir–H bond: Synthesis of new mono- and dinuclear alkyl and alkenyl iridium–pybox complexes

The treatment of the complex [Ir(η2-C2H4)2(L)][PF6] (L = κ3-N,N,N-(S,S)-iPr-pybox) with acetic acid (1:1 molar ratio) at −10 °C affords the complex [Ir(C2H5)(κ2-O,O-O2CCH3)(L)][PF6] (1). The dinuclear iridium(III) complex [Ir2(μ-Cl)2(C2H5)2(L)2][PF6]2 (2) is stereoselectively obtained by spontaneous intramolecular insertion of ethylene into the iridium-hydride bond of the mononuclear complex [IrClH(η2-C2H4)(L)][PF6]. The single bridging chloride dinuclear derivative [Ir2(μ-Cl)(C2H5)2Cl2(L)2][PF6] (3) is prepared by reaction of 2 with one equivalent of NaCl. The intramolecular insertion reaction of methyl and ethyl propiolate into the Ir–H bond of the complex [IrClH(MeCN)(L)][PF6] gives stereoselectively the dinuclear complexes [Ir2(μ-Cl)2(HCdouble bond; length as m-dashCHCO2R)2(L)2][PF6]2 (R = Me (4), Et (5)). The reaction of the complexes 4, 5 with one equivalent of NaCl or with an excess of sodium acetate yields the dinuclear [Ir2(μ-Cl)(HCdouble bond; length as m-dashCHCO2R)2Cl2(L)2][PF6] (R = Me (6), Et (7)) or the mononuclear [IrCl(HCdouble bond; length as m-dashCHCO2Et)(κ1-O-O2CMe)(L)] (8) complexes, respectively. The structure of the dinuclear complex 3 · CH2Cl2 has been determined by an X-ray monocrystal study.