Diphenyllead(IV) chloride complexes with benzilthiosemicarbazones. The first bis(thiosemicarbazone) derivatives

Reactions of diphenyllead(IV) chloride with benzil bis(thiosemicarbazone) (L1H6) and benzil bis(4-methyl-3-thiosemicarbazone) (L1Me2H4) afforded the first complexes containing the diphenyllead(IV) moiety with bis(thiosemicarbazone) ligands. The new complexes show diverse structural characteristics depending on the ligand and the working conditions. Complexes PbPh2Cl(L1H5)].3H2O (1) and PbPh2Cl(L1Me2H3)] (3) are mononuclear species in which the ligands are partially deprotonated and the lead atom has a C2N2S2Cl environment in a distorted pentagonal bipyramid coordination geometry. Complex PbPh(L1Me2H2)](2).2H2O (4) was also obtained, which contains two lead atoms in a binuclear structure with a C2N2S3 coordination sphere for each lead atom, since both dideprotonated ligands act as N2S2 chelate and as sulfur bridge. Reaction from L1H6, in the same conditions in which complex 4 was prepared, gave a mixture of products: the lead (II) complex Pb(L1H4)]2 (2) and PbPh3Cl]n. Reactions with the cyclic molecules 5-methoxy-5,6-diphenyl-4,5-dihydro-2H-1,2,4]-triazine-3-thione (L2H2OCH3) and 5-methoxy-4-methyl-5,6-diphenyl-4,5-dihydro-2H-1,2,4]-triazine-3-thione (L2MeHOCH3) were also explored. In all the complexes, the ligands are deprotonated. The complexes PbPh2(L2)2] (5) and PbPh2(L2MeOCH3)2] (7) present the same characteristics. The X-ray structure of 5 shows a distorted octahedral geometry around the lead atom, with the ligand molecules acting as NS chelates, but the nitrogen bonded to the metal is different; one of the triazines shows a novel behavior, since the nitrogen atom of the new imine group formed is the one that is bonded to the lead center, being a good example of linkage isomerism. The complex PbPh2Cl(L2)] (6), which was also isolated, could not be crystallized. All the complexes were characterized by elemental analysis, mass spectrometry, IR and 1H, 13C, and 207Pb NMR spectroscopy and some of them by X-ray diffraction studies.