First Iridium(IV) Chloride-Dimethyl Sulfoxide Complex [H(dmso) 2 ][IrCl 5 (dmso-κO)]: Synthesis and Structure along with Novel Polymorph Modifications of [H(dmso) 2 ][ trans -IrCl 4 (dmso-κS) 2 ] and [H(dmso)][ trans- IrCl 4 (dmso-κS) 2 ].

As evidenced by UV-Vis and EPR spectroscopies, the reaction of H 2 IrCl 6 ·6H 2 O or Na 2 [IrCl 6 ]· n H 2 O with DMSO results 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 sodium hexachloridoiridate(III), Na 3 [IrCl 6 ]·2H 2 O, as a product of Na 2 [IrCl 6 ]· n H 2 O reduction in an acetone solution. Furthermore, it was shown that [IrCl 5 (Me 2 CO)] - species is gradually formed in an acetone solution of H 2 IrCl 6 ·6H 2 O upon storage. The reaction of DMSO with aged acetone solution of H 2 IrCl 6 ·6H 2 O dominated by [IrCl 5 (Me 2 CO)] - affords a novel iridium(IV) chloride-dimethyl sulfoxide salt [H(dmso) 2 ][IrCl 5 (dmso-κO)] ( 1 ). The compound was characterized by various spectroscopies (IR, EPR, UV-Vis) and X-ray diffraction techniques applied both to single-crystal and polycrystalline powder. The DMSO ligand is coordinated to the iridium site via the oxygen atom. New polymorph modifications of known iridium(III) complexes [H(dmso) 2 ][ trans -IrCl 4 (dmso-κS) 2 ] and [H(dmso)][ trans- IrCl 4 (dmso-κS) 2 ] were isolated and structurally elucidated as byproducts of the above reaction.