Some complex anions containing rhenium

Abstract

Rhenium pentachloride dissolves in 12M hydrochloric acid to give a reddish brown solution from which salts such as Cs₂ReOCl₅ may be isolated. Oxidation of the rhenium occurs if the solution is allowed to stand exposed to the air and salts such as (K,Cs)₂ReOCl₆ may be isolated. These salts of rhenium(VI) have also been isolated by treating a solution of rhenium pentachloride in a thionyl chloride/iodine monochloride mixture with caesium chloride. The complex acid thought to be HReI₅, separated by ether extraction of a solution of potassium hexaiodorhenate(IV) in 20% sulphuric acid, has been shown to be in fact H₂(ReI₅OH) by isolating salts using cations soluble in organic solvents.