Osmium compounds

Oxidation states of osmium −2 −1 0 +1 +2 +3 OsBr3 +4 , +5 +6 +7 +8 ,

Osmium compounds are compounds containing the element osmium (Os). Osmium forms compounds with oxidation states ranging from −2 to +8. The most common oxidation states are +2, +3, +4, and +8. The +8 oxidation state is notable for being the highest attained by any chemical element aside from iridium's +9 and is encountered only in xenon, ruthenium, hassium, iridium, and plutonium. The oxidation states −1 and −2 represented by the two reactive compounds and are used in the synthesis of osmium cluster compounds.

Osmium tetrabromide is a black solid that can be produced by heating osmium tetrachloride and bromine under pressure. As determined by X ray crystallography, osmium tetrabromide is an inorganic polymer. It is isomorphous with platinum tetrabromide and technetium tetrachloride. As such, osmium is in octahedral coordination. Each osmium center bonds to four doubly bridging bromide ligands and two mutually cis terminal bromide ligands. Osmium tribromide, OsBr3, is the only other binary osmium bromide is that has been crystallized.

Osmium(I) iodide is a metallic grey solid produced by the reaction of osmium tetroxide and hydroiodic acid heated in a water bath for 48 hours in a carbon dioxide atmosphere. It is an amorphous compound. Osmium(II) iodide is a black solid Osmium(III) iodide is a black solid that is produced by heating hexaiodoosmic acid (H2OsI6).) produced dihydroxonium hexaiodoosmate instead of the tetraiodo compound, and instead contained mono, di and tri iodo osmium compounds. These borides are produced in vacuum or inert atmosphere to prevent formation
of osmium tetroxide, which is a hazardous compound. Synthesis occurs at high temperatures (~1000 °C) from a mixture of MgB2 and OsCl3. similar to that of rhenium diboride. Osmium diboride was first also sought as hexagonal, but one of its phases was later reassigned to orthorhombic. In recent methods of synthesis, it has also been found that a hexagonal phase of OsB2 exists with a similar structure to ReB2.