Syntheses and X-ray characterization of metal complexes with the pentadentate thiosemicarbazone ligand bis(4-N-methylthiosemicarbazone)-2,6-diacetylpyridine.: The first pentacoordinate lead(II) complex with a pentagonal geometry

In this paper we describe the electrochemical synthesis and characterization of new neutral manganese, iron, cobalt, nickel, copper, zinc, cadmium and lead complexes with the ligand bis( 4- N - methylthiosemicarbazone) - 2,6-diacetylpyridine, H(4)DAPTsz- Me. X- Ray structures of [ Mn( H(2)DAPTsz- Me) ( EtOH) (2)] 1, [ Pb( H(2)DAPTsz- Me)] 3 and [ Zn( H(2)DAPTsz- Me)] (2) . EtOH . 2H(2)O 4, were also determined. In these complexes the ligand behaves as bis- deprotonated and SNNNS pentadentate. In the manganese complex the metal is heptacoordinated, in a distorted pentagonal- bipyramidal environment, with the N3S2 donor set of the ligand in the pentagonal girdle and two solvent molecules occupying the axial positions. In the lead complex 3 the metal is pentacoordinated, bound exclusively to the five donor atoms of the ligand, as a consequence of the existence of inert pair effect. The bishelical zinc complex 4 shows each zinc atom with different coordination geometry, one octahedrally six- coordinate while the other is distorted tetrahedrally four- coordinate.