Osmium(IV) Halide Complexes with Dimethyl Sulfoxide[H(dmso)(2)][OsX5(dmso-kappa O)], X=Cl, Br: Synthesis, Structure, and Properties

Two osmium complexes of common formula [H(dmso)(2)][(OsX5)-X-IV(dmso-kappa O)] 1 (X=Cl) and 2 (X=Br) are synthesized via the reaction of H2OsX6 (X=Cl, Br) with DMSO. The complex 1 crystallized in the orthorhombic space group Pca2(1). For 2, two orthorhombic polymorphs are found, namely, 2 a in space group Cmcm and 2 b in space group Pbca. Within the [H(dmso)(2)](+) cations of 1 and 2 a, the cis-configuration of the DMSO moieties has been observed for the first time. The complexes are characterized by a set of spectroscopic (NMR, IR, UV-Vis, EXAFS/XANES) and diffraction (single crystal and powder) techniques. Both complexes 1 and 2 retain their molecular structures in DMSO and acetone solutions, as evidenced by Os L-3-edge EXAFS/XANES. H-1 NMR spectra of 1 and 2 in DMSO solutions reveal signals of coordinated DMSO. In acetone solutions, signals of the [H(dmso)(2)](+) cations are observed in addition to those of coordinated neutral DMSO.