Cobalt(II) phosphate

Cobalt phosphate is the inorganic compound with the formula Co3(PO4)2. It is a commercial inorganic pigment known as cobalt violet. Thin films of this material are water oxidation catalysts.


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Preparation and structure
The tetrahydrate Co3(PO4)2•4H2O precipitates as a solid upon mixing aqueous solutions of cobalt(II) and phosphate salts. Upon heating, the tetrahydrate converts to the anhydrous material. According to X-ray crystallography, the anhydrous Co3(PO4)2 consists of discrete phosphate anions that link  centres. The cobalt ions occupy both octahedral (six-coordinate) and pentacoordinate sites in a 1:2 ratio.