A route to various substituted phosphine phosphonic acid compounds of the general form Ar2PC6H4PO (OH) 2 (Ar= Ph, o-MeC6H4, o-MeOC6H4) has been investigated. These compounds were employed as bidentate anionic [P, O] ligands in neutral palladium complexes. The [P, O] chelating coordination was determined by X-ray crystallography of a representative palladium complex. Furthermore, the bifunctional ligand Ph2PC6H4PO ( ...