First Iridium(IV) Chloride-Dimethyl Sulfoxide Complex [H(dmso)₂][IrCl₅(dmso-O)]: Synthesis and Structure along with Novel Polymorph Modifications of [H(dmso)₂][trans-IrCl₄(dmso-S)₂ ] and [H(dmso)][trans-IrCl₄(dmso-S)₂]

As evidenced by UV-Visand EPR spectroscopies, the reactionof H2IrCl6 center dot 6H(2)O or Na-2[IrCl6]center dot nH(2)O with DMSOresults in a slow reduction of Ir-(IV) avoiding the formation of Ir-(IV)dimethyl sulfoxide complexes in measurable quantities. More specifically,we successfully isolated and solved the crystal structure of a sodiumhexachloridoiridate-(III), Na-3[IrCl6]center dot 2H(2)O, as a product of Na-2[IrCl6]center dot nH(2)O reduction in an acetone solution. Furthermore,it was shown that [IrCl5(Me2CO)](-) species is gradually formed in an acetone solution of H2IrCl6 center dot 6H(2)O upon storage. The reactionof DMSO with aged acetone solution of H2IrCl6 center dot 6H(2)O dominated by [IrCl5(Me2CO)](-) affords a novel iridium-(IV) chloride-dimethylsulfoxide salt [H-(dmso)(2)]-[IrCl5(dmso-kappa O)](1). The compound was characterized by various spectroscopies(IR, EPR, UV-Vis) and X-ray diffraction techniques appliedboth to single-crystal and polycrystalline powder. The DMSO ligandis coordinated to the iridium site via the oxygen atom. New polymorphmodifications of known iridium-(III) complexes [H-(dmso)(2)]-[trans-IrCl4(dmso-kappa S)(2)] and [H-(dmso)]-[trans-IrCl4(dmso-kappa S)(2)] were isolated and structurally elucidated as byproductsof the above reaction.