Phosphorus Pentaselenide, P₂Se₅

Phosphorus Pentaselenide or Phosphoric Selenide, P₂Se₅, may be prepared by melting together phosphorus and selenium in the atomic proportions until combination takes place.

It is a reddish-brown solid, insoluble in carbon disulphide. It dissolves in carbon tetrachloride on heating, from which solution it crystallises out in black needles on cooling. It is decomposed by heat and burns, leaving a residue of selenium. It combines with the selenides of certain metals, e.g. copper and silver, forming double selenides.

Attempts to prepare phosphorus thioselenides from the components in tetrahydronaphthalene, in a manner similar to that used for tetraphosphorus triselenide, have failed to produce any definite compounds.