The first tris(saccharinato) complexes. Syntheses, spectral, thermal and structural characterization of ApyH[Cu(N?sac)2(O?sac)(H2O)2] and ApyH[Zn(N?sac)3- (H2O)] (ApyH=2?aminopyridinium and sac=saccharinate)

Abstract

The reaction of the Schiff base salicylideneaminopyridine with [M(sac)2(H2O)4] · 2H2O, where M is copper(II) or zinc(II), and sac is the saccharinate anion, results in the formation of the new tris(saccharinato) complexes ApyH[Cu(N-sac)2(O-sac)(H2O)2] (1) and ApyH[Zn(N-sac)3(H2O)] (2), which have been characterized by elemental analyses, magnetic measurements, FT-IR spectroscopy, thermal analysis and X-ray diffraction. The Schiff base did not coordinate to the metal ions, but decomposed during the reaction, forming a 2-aminopyridinium cation ApyH, which remained outside the coordination sphere as a counter ion. (1) and (2) are the first examples of mononuclear tris(saccharinato) complexes of copper(II) and zinc(II). Both complexes are isomorphous with the triclinic space group P-1, (1) consisting of an ApyH cation and a [Cu(sac)3(H2O)2]− anion in which the copper(II) ion has trigonal bipyramidal surroundings. The sac ligands in (1) exhibit unusual and non-equivalent coordination, behaving as ambidentate ligands. One of them coordinates to the metals through the carbonyl oxygen atom, while the other two sac ligands are bonded to the metals via the imino nitrogen atom. The zinc(II) ion in (2) is tetrahedrally coordinated by three N-donor sac ligands and an aqua ligand. The crystal structures of (1) and (2) are stabilized by intermolecular hydrogen bonds and aromatic π–π stacking interactions.