Oxovanadium(IV) perchlorate is an inorganic compound containing the vanadyl ion, VO2+, and perchlorate anions, with the formula VO(ClO4)2. It is usually encountered in hydrated form or in aqueous solution. The pentahydrate, VO(ClO4)2·5H2O, is a well-characterized form.
Preparation Oxovanadium(IV) perchlorate can be prepared from vanadyl sulfate by metathesis with a soluble perchlorate salt. For example, aqueous vanadyl sulfate and barium perchlorate react to precipitate insoluble barium sulfate, leaving oxovanadium(IV) perchlorate in solution:
VOSO4 + Ba(ClO4)2 → VO(ClO4)2 + BaSO4↓
The resulting solution can be concentrated by evaporation.
An older preparation used vanadium(IV) hydroxide and approximately 3.5 N perchloric acid.
Properties Hydration and aqueous structure The pentahydrate, VO(ClO4)2·5H2O, dissolves readily in water. In dilute aqueous solution the vanadium(IV) centre is present predominantly as the pentaaquaoxovanadium(IV) ion, [VO(H2O)5]2+, with perchlorate acting mainly as a non-coordinating counterion.
Modern structural and spectroscopic studies of aqueous VO(ClO4)2 likewise support a strongly hydrated VO2+ cation with weak perchlorate coordination in water.
The characteristic blue colour of its aqueous solutions is due to the d1 oxovanadium(IV) ion.
Coordination chemistry Oxovanadium(IV) perchlorate is commonly used as a source of VO2+ in coordination chemistry because perchlorate is only weakly coordinating.
Addition of dimethyl sulfoxide to concentrated aqueous VO(ClO4)2 gives the complex [VO(DMSO)5](ClO4)2. Similar complexes are known with other oxygen-donor ligands.
A methyl phenyl sulfoxide complex of composition VO(ClO4)2·4MPSO has also been reported.
Oxovanadium(IV) perchlorate has therefore been widely used as a precursor to other vanadyl complexes.
Safety Oxovanadium(IV) perchlorate is an oxidizing perchlorate salt. Contact with combustible or strongly reducing materials should be avoided.
References