THE PREPARATIVE AND STRUCTURAL CHEMISTRIES OF HEXAHALOGENO AND TRICHLOROSTANNATO COMPLEXES OF IRIDIUM

In a study of Ir(III) and Ir(IV) halogeno complexes it was found that oxidation of Ir(III) to Ir(IV) occurs readily, even in the presence of reducing agents such as tin(II) halides and from solutions containing predominantly the trivalent oxidation state. The three cubic (Fm3m) hexahalogenoiridates(IV) complexes; oxonium hexabromoiridate(IV), (H3O)2[IrBr6], a = 1027.4(3) pm, Ir-Br = 251.5(1) pm; ammonium hexabromoiridate(IV), (NH4)2[IrBr6], a = 1044.0(2) pm, Ir-Br = 254.9(3) pm; and caesium hexachloroiridate(IV), Cs2[IrCl6], a = 1021.19(8) pm, Ir-Cl = 233.2(2) pm, were isolated from the solutions, and their single crystal and molecular structures determined. The iridium(III) and rhodium(III) trichlorostannato complexes A3[IrCl5(SnCl3)] for A = K+, NH4+, and Rb3[RhCl3(SnCl3)3] have been prepared. The single crystal X-ray structure has been determined for K3[IrCl5(SnCl3)]. The complex and the isomorphous NH4+ salt belong to the orthorhombic crystal system a = 958.73(13), b = 951.70(15), c = 784.80(9) pm, with space group Pmn2(1). The molecule has m symmetry and the Ir-Cl bond length for the chlorine atom bound opposite the SnCl3- ligand is longer at 243.8(3) pm compared with the other Ir-Cl bond lengths which lie in the range 233.9(3)-237.6(2) pm. The Ir-Sn bond length of 249.6(1) pm is relatively short compared with other reported values.