Structural and spectral studies of a heterocyclic N(4)-substituted bis(thiosemicarbazone), H(2)2,6Achexim center dot H2O, its heptacoordinated tin(IV) complex [Bu2Sn(2,6Achexim)], and its binuclear zinc(II) complex [Zn(2,6Achexim)](2)

The multidentate ligand, 2,6-diacetylpyridine bis(3-hexamethyleneiminylthio semicarbazone) monohydrate, H(2)2,6Achexim . H2O, crystallizes with one thi osemicarbazone moiety in an intramolecular hydrogen bonded, bifurcated E' f orm. The other thiosemicarbazone moiety is E and is not involved in intramo lecular hydrogen bonding, but is involved in hydrogen bonding with the hydr ate water molecule. The dianion (loss of N3a and N3b hydrogens) of H(2)2,6A chexim acts as a pentadentate ligand, 2,6Achexim, in a planar conformation to a central tin(IV) ion, and as a bridging tetradentate ligand with the tw o thiosemicarbazone moieties of 2,6Achexim coordinating to different zinc a toms. The tin(IV) is heptacoordinate in a distorted pentagonal dipyramidal configuration, with the five SNNNS donor atoms of 2,6Achexim in the pentago nal plane and the two n-butyl groups in the axial positions. The binuclear zinc complex has two equivalent tetrahedral zinc centers, with the pyridyl nitrogens of the two ligands not coordinated. (C) 2000 Elsevier Science Ltd All rights reserved.