PI-OLEFIN-IRIDIUM COMPLEXES .2. SYNTHESIS AND DYNAMIC BEHAVIOR OF BIS-(ETA4-CYCLODIENE)HYDRIDO-IRIDIUM(I) COMPLEXES

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. © 1979.