Different coordination modes of saccharin in the metal complexes with 2-pyridylmethanol: synthesis, spectroscopic, thermal and structural characterization

Abstract

The reaction of [M(sac)(2)(H(2)O)].2H(2)O(2) where M is Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II), and sac is the saccharinate anion, with 2-pyridylmethanol (mpy) result in the formation of the new complexes, which have been characterized by elemental analyses, magnetic measurements, FT-IR spectroscopy, thermal analysis and X-ray diffraction methods. The [Co(sac)(2)(mpy)(2)] (3) and [Ni(sac)(2)(mpy)(2)] (4) complexes are isomorphous with the triclinic space group the two sac ligands in both 3 and 4 exhibit unusual and non-equivalent coordination. One of them coordinates to the metals through the imino nitrogen atom, while the other is bonded to the metals with the carbonyl oxygen atom behaving as an ambidentate ligand. The [Cu(sac)(2)(mpy)(2)] (5) complex is centrosymmetric and crystallizes in ortborhombic space group and both sac ligands in (5) are N-coordinated. [Hg(2)(saC)(4)(MPY)(2)] (8) crystallizes in monoclinic space group P2(1)/n. In 8, the mpy ligands acts as a bridge between the mercury two mercury(II) centres and the complex 8 consists of one-dimensional chains in which dimeric [Hg(2)(sac)(4)(mpy)(2)] units are sequentially bridged by bis-bidentate sac ligands forming a coordination polymer. In all cases, the metal atoms are six-coordinate. The mpy molecules act as a bidentate N- and O-donor ligand in 1-7. Thermal decomposition of the complexes in air results in removal of mpy ligands and formation of stable metal saccharinates as intermediates, which also decompose at higher temperatures to give the corresponding metal oxides. (C) 2002 Elsevier Science Ltd. All rights reserved.