Electrospray ionization mass spectrometry in the structural characterization of some diphenyllead(IV) thiosemicarbazonates.

The behavior in electrospray ionization mass spectrometry (ESI-MS) conditions of some complexes formed by Pb(C6H5)2(OAc)2 with salicylaldehyde, 2-ketobutyric acid, pyridine-2-carbaldehyde, 2-acetylpyridine, and 2-benzoylpyridine thiosemicarbazones, was studied in detail with the aid of collisional experiments performed by ion trap. The homoleptic complexes of tridentate thiosemicarbazonate dianions (TSC2-) lose the phenyl groups first, destabilizing the high oxidation state of the metal and leading to Pb(II) complexes in which the TSC2- ligand or a part of it remains coordinated to the metal. The main difference among the complexes derives from the presence of a carboxylate group on the 2-ketobutyric acid thiosemicarbazonato ligand, which probably interacts with a Na+ cation leading to ESI-generated [M+Na]+ species. In the absence of the carboxylate group, the production of abundant protonated molecules is observed. These different behaviors have been rationalized from the structural point of view. The heteroleptic mononuclear complexes, including thiosemicarbazonate and AcO- monoanions in the coordination sphere, do not yield intact ionized molecular species, and the most abundant ESI-generated ion is due to AcO- loss. The spectrum of the binuclear heteroleptic complex formed by the salicylaldehyde thiosemicarbazonate monoanion is conditioned by the weak bonding interaction displayed by the acetate bridge. MSn experiments yield important information on the relative ligand-Pb bond strengths. This work forms part of the search for chelating agents that can be used for effective chemotherapy of organolead poisoning.

Compositional and structural variety of diphenyllead(IV) complexes obtained by reaction of diphenyllead dichloride with thiosemicarbazones.

The reactions of PbPh(2)Cl(2) in methanol with acetophenone, salicylaldehyde, pyridine-2-carbaldehyde, 2-acetylpyridine, and 2-benzoylpyridine thiosemicarbazones (HATSC, HSTSC, HPyTSC, HAcPyTSC, and HBPyTSC, respectively) were explored. Despite the similarities among these ligands, the reactions afforded solids with very diverse compositions and structural characteristics, which were in most cases analyzed by X-ray diffractometry (as was the structure of the free ligand HBPyTSC). In the complexes [PbPh(2)Cl(2)(HATSC)](2), [PbPh(2)Cl(2)(HSTSC)(2)], [(PbPh(2)Cl(HPyTSC)(2))][PbPh(2)Cl(3)(MeOH)](2), and [PbPh(2)Cl(PyTSC)] the metal atoms are surrounded by more or less distorted octahedral coordination polyhedra; if both strong and weak interactions are considered, the lead atom in [PbPh(2)Cl(AcPyTSC)] has coordination number 7 and distorted pentagonal bipyramidal coordination geometry, while [(PbPh(2)(BPyTSC))(2)(PbPh(2)Cl(4))].2MeOH contains two different types of lead atom, one with octahedral and the other with pentagonal bipyramidal coordination. The complexes (H(2)AcPyTSC)[PbPh(2)Cl(3)] and [PbPh(2)Cl(HAcPyTSC)][PbPh(2)Cl(3)], which were also isolated, could not be crystallized. All these complexes are soluble in DMSO, and the compositions of these solutions were investigated using conductivity measurements and (1)H and (207)Pb NMR spectroscopy.