Cuprous phosphide, Cu₃P

Phosphine reacts with heated copper cuprous oxide, chloride, or sulphide, forming a black powder, Cuprous phosphide, Cu₃P density 6.59 to 6.75, also produced by reducing cupric phosphide with hydrogen. Other phosphides of the formulae CuP, Cu₂P, Cu₅P, and Cu₆P have been described, but their existence is doubtful.