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

Abstract

The treatment of the complex [Ir(η 2-C 2H 4) 2(L)][PF 6] (L = κ 3- N, N, N-( S, S)- i Pr-pybox) with acetic acid (1:1 molar ratio) at −10 °C affords the complex [Ir(C 2H 5)(κ 2- O, O-O 2CCH 3)(L)][PF 6] ( 1). The dinuclear iridium(III) complex [Ir 2(μ-Cl) 2(C 2H 5) 2(L) 2][PF 6] 2 ( 2) is stereoselectively obtained by spontaneous intramolecular insertion of ethylene into the iridium-hydride bond of the mononuclear complex [IrClH(η 2-C 2H 4)(L)][PF 6]. The single bridging chloride dinuclear derivative [Ir 2(μ-Cl)(C 2H 5) 2Cl 2(L) 2][PF 6] ( 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)][PF 6] gives stereoselectively the dinuclear complexes [Ir 2(μ-Cl) 2(HC CHCO 2R) 2(L) 2][PF 6] 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 [Ir 2(μ-Cl)(HC CHCO 2R) 2Cl 2(L) 2][PF 6] (R = Me ( 6), Et ( 7)) or the mononuclear [IrCl(HC CHCO 2Et)(κ 1- O-O 2CMe)(L)] ( 8) complexes, respectively. The structure of the dinuclear complex 3 · CH 2Cl 2 has been determined by an X-ray monocrystal study.