Synthese und Struktur von Ammin- und Amidokomplexen des Iridiums

Synthesis and Structure of Ammine and Amido Complexes of Iridium The reaction of (NH₄)₂IrCl₆] with NH₄Cl at 300 °C in a sealed glass ampoule yields the iridium(III) ammine complex (NH₄)₂Ir(NH₃)Cl₅], which crystallizes isotypically with K₂Ir(NH₃)Cl₅] in the orthorhombic space group Pnma with Z = 4, and a = 1350.0(2); b = 1028.5(3); c = 689.6(2) pm. The reaction of (NH₄)₂IrCl₆] with NH₃ at 300 °C, however, gives the already known Ir(NH₃)₅Cl]Cl₂ beside a small amount of Ir(NH₃)₄Cl₂]Cl₂. In pure form Ir(NH₃)₅Cl]Cl₂ is obtained by ammonolysis of (NH₄)₂Ir(NH₃)Cl₅] at 300 °C with NH₃. Ir(NH₃)₄Cl₂]Cl₂ crystallizes triclinic (P1, Z = 1, a = 660,2(3); b = 680,4(3); c = 711,1(2) pm; α = 103,85(2)°, β = 114,54(3)°, γ = 112,75(2)°). The structure contains Cl^– anions and Ir(NH₃)₄Cl₂]²⁺ cations with a trans position of the Cl atoms. Upon reaction of Ir(NH₃)₅Cl]Cl₂ with Cl₂ one ammine ligand is eliminated yielding Ir(NH₃)₄Cl₂]Cl, which is transformed to orthorhombic Ir(NH₃)₄(OH₂)Cl]Cl₂ (Pnma, Z = 4, a = 1335,1(3); b = 1047,9(2); c = 673,4(2) pm) by crystallization from water. In the octahedral complex Ir(NH₃)₄(OH₂)Cl]²⁺ the four ammine ligands have an equatorial position, whereas the Cl atom and the aqua ligand are arranged axial. Oxidation of (NH₄)₂Ir(NH₃)Cl₅] with Cl₂ at 330 °C affords the tetragonal Ir^IV complex (NH₄)Ir(NH₃)Cl₅] (P4nc, Z = 2, a = 702.68(5); c = 912.89(9) pm). Its structure was determined using the powder diagram. Oxidation of (NH₄)₂Ir(NH₃)Cl₅] with Br₂ in water, on the other hand, gives (NH₄)₂IrBr₆] crystallizing in the K₂PtCl₆] type. Oxidation of (PPh₄)₂Ir(NH₃)Cl₅] with PhI(OAc)₂ in CH₂Cl₂ affords the Ir^V amido complex (PPh₄)Ir(NH₂)Cl₅].