Ammonium hexachloroosmate(IV) is an inorganic chemical compound with the chemical formula .
Synthesis Ammonium hexachloroosmate(IV) can be produced by the reduction of osmium tetroxide with iron dichloride in hydrochloric acid in the presence of ammonium ions:
It can also be prepared by addition of an ammonium chloride solution to hexachloroosmic acid, or by addition of ammonium chloride to a solution of sodium hexachloroosmate.
Physical properties Ammonium hexachloroosmate(IV) forms dark red crystals of the cubic system, space group Fm3m, cell parameters a = 0.9729 nm, Z = 4.
It dissolves sparingly in water to form greenish-yellow solutions. It is insoluble in alcohol.
Chemical properties The compound is reduced by hydrogen to metallic osmium:
Ammonium hexachloroosmate is stable in hydrochloric acid, but it is oxidized by nitric acid, forming osmium tetroxide. When exposed to strong alkali, it reacts to produce osmium oxydiammine dihydroxide, .
It can hydrolyze, whereby it forms osmium dioxide. It can also undergo a reversible aquation, producing the aquopentachloroosmate anion.
Reactions Ammonium hexachloroosmate reacts with triphenylphosphine to form various complexes in which osmium is divalent.
+ 4 + 2 + 2
+ 6 + 2 + 3
It also reacts with triphenylphosphine in a solution of t-butyl alcohol and water to produce .
When ammonium hexachloroosmate is refluxed with diethylphenylphosphine, is formed.
It reacts with hydrazine hydrate to form a variety of different products, chief of which are and .
Uses The compound is used as a pharmaceutical, organic, and chemical intermediate.
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