Osmium dimethyl sulfoxide complexes: Synthesis and properties of [H(dmso)2][OsIII(dmso)2Br4

Abstract

The reaction of H2[OsBr6] with DMSO in ethanol solution resulted in DMSO complex [H(dmso-O)2][OsIII(dmso-S)2Br4] (1) described previously as an intermediate product in the reaction of K2[OsBr6] with DMSO and characterized by EAS and ESR spectra. The coordination of DMSO molecules was established by IR and 1H and 13C NMR spectroscopy. The oxidation state of osmium and trans arrangement of DMSO molecules in the anion were established by ESR. The behavior of complex 1 in solutions was studied by EAS, ESR, and mass-spectrometry: a displacement of Br− ions accompanied by the reduction of osmium to oxidation state +2 occurs in DMSO, a solvation with displacement of DMSO molecules is observed at the first stage in water and methanol (rate constants 2.3 × 10−4 and 1.7 × 10−3 s−1, respectively), the sequential substitution of DMSO molecules and osmium oxidation to form [OsIVBr6]2− ions takes place in 4 mol/L HBr.