Abstract A model study of alkaline hydrolysis of β-and γ-heterosubstituted phosphonium salts has been made and used as a synthetic method to obtain diphosphine dioxides affording additional coordination sites in an alkyl chain linked to phosphorus. After synthesis of the corresponding salts, anomalous fragmentations, such as inversion in cleavage selectivity or participation of the reaction solvent, have been pointed out in alkaline ...