Copper(II) phosphate is an inorganic compound with the chemical formula Cu<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>. It can be regarded as the cupric salt of phosphoric acid. Anhydrous copper(II) phosphate and a trihydrate are blue solids.
Copper(II) phosphate is relatively commonly encountered as the hydrated species Cu<sub>2</sub>(PO<sub>4</sub>)OH, which is green and occurs naturally as the mineral libethenite. Pseudomalachite, Cu<sub>5</sub>(PO<sub>4</sub>)<sub>2</sub>(OH)<sub>4</sub>, is the most common copper phosphate in nature, typical for some oxidation zones of copper ore deposits.
In terms of structure, copper(II) phosphate is a coordination polymer, as is typical for most metal phosphates. The phosphate center is tetrahedral. In the anhydrous material, the copper centers are pentacoordinate. In the monohydrate, the copper adopts 6-, 5-, and 4-coordinate geometries.
Hydrated copper(II) phosphate precipitates upon addition of a solution of alkali metal phosphate to an aqueous solution of copper(II) sulfate. The anhydrous material can be produced by a high-temperature (1000 ðC) reaction between diammonium phosphate and copper(II) oxide.
In laboratories, copper phosphate is prepared by the addition of phosphoric acid to an alkali copper salt such as copper hydroxide, or basic copper carbonate.
Copper(II) phosphate has many uses. Due to it being a copper metal salt it can be used as a fungicide; it works by denaturating proteins and enzymes in cells of pathogens. Many other copper salts, such as copper sulfate, are used as fungicides.
Another use of copper(II) phosphate is as a fertilizer. Copper is one of the 16 essential elements required for plant growth. Copper(II) phosphate supplies the plant with both phosphorus and copper, which stimulates growth.