π-Olefin-iridium-komplexe : II. Synthese und dynamisches verhalten von bis(η4-Cyclodien)-hydrido-iridium(I)-komplexen

By reaction of Ir(COD)Cl]₂ (COD = 1,5-cyclooctadiene) with i-C₃H₇MgBr in the presence of cyclic dienes, complexes of the type IrH(COD)L] (L = 1,3-cyclohexadiene, 2-methyl-],3-cyclohexadiene, 5-ethyl-1,3-cyclohexadiene, 1,3-cycloheptadiene) are obtained. The system IrCl₃/i-C₃H₇MgBr/1,3-C₆H₈ yields IrH(1,3-C₆H₈)₂]. According to NMR spectroscopic investigations the pure hydrido forms exist in solution only at low temperatures while at room temperature dynamic H-addition—elimination equilibria of the type IrH(η⁴-diene)(COD)] ? Ir(η³-enyl)(COD)] and IrH(η⁴-1,3-C₆H₈)₂] ? Ir(η³-C₆H₉)-(η⁴-1,3-C₆H₈)], respectively, are observed; the hydrogen at the iridium atom is thereby transferred to the endo positions of the diene ligands.