or exo-cyclic nitrogenatom. The two tautomers show different reactivities toward alcoholysis; the imino form degrades more rapidly. Their bischelated platinum complexes were studied in the solidstate by single crystal X-ray diffraction. Thus, the unique stereoelectronic features of the [Pt(PN(th))] (PN(th)=diphenylposphino-aminothiazoline) moiety were revealed. The complex cis-[Pt(PN(th))(2)] reacts