Blue Osmium(IV) Sulfite Complex: Synthesis and Study

Blue osmium(IV) sulfite complex Na4[Os2(μ-O)2(SO3)4(H2O)4] · 4.5 H2O was synthesized via the reaction of aqueous solutions containing OsO4 and equimolar amount of Na2SO3 and H2SO4 at 50°C and its composition and structure were determined by elemental analysis, X-ray electronic and IR spectroscopies, and thermogravimetric analysis. The compound is X-ray amorphous, insoluble in water but soluble in hydrochloric and sulfuric acids. The electrochemical methods (cyclic voltammetry and potential-controlled coulometry) indicate the complex polymerization in solutions. Under continuous electrolysis at high negative potentials (Er = –0.10 V), the product under study is depolymerized and the monomeric Os(II) complexes are formed. At a high positive potential (E0 = 1.00 V), Os(VI) is formed that disproportionates into Os(IV) and Os(VIII).