Synthesis and structure of [H(DMSO)2]2[OsX6] (X = Cl, Br)

The reactions of H2OsX6 · nH2O (X = Cl, Br) with dimethyl sulfoxide (DMSO) or DMSO-d6 in acetone afford the osmium(IV) complexes: [H(DMSO-O)2]2[OsCl6] (I), [H(DMSO-O)2]2[OsBr6] (II), [H(DMSO-d6)2]2[OsCl6] (Ia), and [H(DMSO-d6)2]2[OsBr6] (IIa). According to the X-ray diffraction data (CIF files CCDC 997574 (I) and 997575 (II)), the crystals of compounds I and II are isostructural, triclinic, space group $$P\bar 1$$ , a = 7.7732(2), b = 8.9209(3), c = 9.8176(3) Å, α = 69.0120(10)°, β = 72.2170(10)°, γ = 67.4330(10)°, Z = 1 (I); a = 7.9241(4), b = 9.1701(5), c = 10.2644(5) Å, α = 67.5250(10)°, β = 71.0670(10)°, γ = 66.5990(10)°, Z = 1 (II). The compounds consist of cations [H(DMSO)2]+ with a very strong hydrogen bond O⋯H⋯O (O⋯O 2.441 Å in I and 2.457 Å in II; the hydrogen atom is predominantly localized at one oxygen atom) and anions [OsX6]2−, being somewhat distorted octahedra. The synthesized complexes are characterized by IR spectroscopy, UV/Vis spectroscopy, NMR spectroscopy, and potentiometry. In DMSO solutions, cations [H(DMSO)2]+ dissociate and DMSO enters the internal sphere of the anions to form the DMSO complexes of osmium(III) and osmium(II).