Woollins' reagent (WR, (PhPSe2)2) plays an essential role in the selenation of organic compounds. Reaction of WR with pyridine gives the P(V) species PhPSe2 stabilised by pyridine coordination which is the first crystallographically characterised mononuclear RPSe2 system stabilised by an external molecule and has potential as a selenation reagent for reactions under mild conditions.