Triphenylmethyl fluoride 1 will effect chlorine–fluorine exchange in certain phosphorus chlorides. Exchange of chlorine for fluorine was observed only in σ 3 λ 3 (P)- and σ 5 λ 5 (P)-compounds, while phosphorus oxychloride as an example of a σ 4 λ 5 (P)-compound was unreactive towards 1.