The Chelating Behaviour of 3-(4-X-Phenyl)-2-sulfanylpropenoic Acids with the PbII Ion - Relevance of the Lone Electron Pair in the Supramolecular Structures of the 2:1 Complexes

The interaction of 3‐(4‐X‐phenyl)‐2‐sulfanylpropenoic acids [H2(X‐pspa); X = –F, –Cl, –Br, –I, –OCH3, –OCF3, –OH] with lead(II) acetate in an alcoholic medium was explored in the search for new chelating agents for the Pb2+ ion. The direct reactions afforded [Pb(X‐pspa)] complexes in yields of 67 (X = –Br) to 95 % (X = –OCH3). When the PbII/H2(X‐pspa) reaction was performed in the presence of diisopropylamine (Q), the derivatives [HQ]2[Pb(X‐pspa)2] (X = Cl, Br) were obtained. All of the complexes were characterized by spectrometric (FAB‐MS and ESI‐MS) and spectroscopic (IR, 1H and 13C NMR spectroscopy) methods and these showed the permanence of the O,S coordination of the ligands to the metal ion in dimethyl sulfoxide (DMSO) solution. H2(Cl‐pspa), [HQ]2[Pb(Cl‐pspa)2] and [HQ]2[Pb(Br‐pspa)2] were also fully characterized in the solid state by X‐ray diffraction. The importance of the stereochemically active lone electron pair of the PbII ion in the supramolecular arrangement of [HQ]2[Pb(X‐pspa)2] (X = Cl, Br) is discussed. The characteristics of complexes formed by 3‐(4‐X‐phenyl)‐2‐sulfanylpropenoic acids with lead(II) cations have been explored both in the solid state and in solution. The importance of the stereochemically active lone electron pair of the PbII ion in the supramolecular arrangement of [HQ]2[Pb(X‐pspa)2] (X = Cl, Br; Q = diisopropylamine) is discussed.