Complexation behaviour of hexadentate ligands possessing N2O4 and N2O2S2 cores: differential reactivity towards Co(II), Ni(II) and Zn(II) salts and structures of the products

Reactions of divalent metal salts of Co, Ni and Zn with 1,2-di(salicylaldimino-o-phenylthio) ethane (H2L1) and 1,2-di(naphthaldimino-o-phenylthio) ethane (H2L2), having N2O2S2 cores, and 1,2-di(O-salicylaldimino-o-hydroxyphenyl) ethane (H2L3), having a N2O4 core, have been explored. Out of the three ligands and the nine products obtained from the corresponding reactions, two ligands and seven products were crystallographically characterized. However, all the ligands and the products were characterized by analytical and spectral methods. Reaction of H2L1 and H2L2 with Co(II) salts results in oxidative cleavage of the C-S bond to produce a Co(III) product bound to two dissimilar tridentate ligands formed as a result of the cleavage. The reaction of H2L1 and H2L2 with Co(III) acac in the presence of methanolic NaOH also shows cleavage of the C-S bond to give compounds similar to those obtained by reacting H2L1 and H2L2 with Co(II) salts in the absence of additional external base. However, the reaction of Co(II) salt with H2L3 did not lead to any C-O bond cleavage; rather it produced an octahedral Co(II) complex of the hexadentate H2L3. Reactions of all these three ligands with Ni(II) salt resulted in octahedral complexes of the corresponding hexadentate ligands. In the case of Zn(II), while H2L3 with a N2O4 core resulted in an octahedral complex, H2L1 and H2L2, both with a N2O2S2 core, produced pseudo-octahedral complexes whose Zn-S bond lengths are rather long. The conformations of both the 5-membered and 6-membered chelate rings formed in the products were evaluated. The extent of distortion exhibited in the geometry of these octahedral complexes was computed and appropriately compared

Crystal structure of 4,6-O-ethylidene-N-(2-hydroxybenzylidene)-β-D-glucopyranosylamine

4,6-O-Ethylidene-N-(2-hydroxybenzylidene)-β-D-glucopyranosylamine was synthesized and characterized using analytical, spectral and single-crystal X-ray diffraction methods. The anomeric nature of the saccharide moiety was proposed based on 1H NMR studies and was confirmed by the crystal structure. The lattice structure of this compound was compared with that of its analogues.© Elsevie

Synthesis, structural diversity, inter-conversion and reactivity of Cu(II) complexes of hydroxy-rich molecules

Tetranuclear Cu(II) complexes having linear, cubane and pseudodouble-cubane cores were synthesized using hydroxy-rich molecules possessing amine and imine groups. The products were structurally characterized and were studied for their ability to oxidize catechol as well as for their inter-conversion between mono- and tetra-nuclear complexes

Mono-, di- and tri-nuclear Ni(II) complexes of N-, O-donor ligands: structural diversity and reactivity

A series of mono-, di- and tri-nuclear Ni(II) complexes of N, O-donating molecules possessing ---H2C---NH--- and ---HC=N--- moieties have been synthesized and characterized and the structures have been determined by single crystal X-ray diffraction. All these exhibited interesting molecular packing in their crystal lattices. Di-nuclear complexes were found to be cleaved in pyridine to result in mononuclear ones with additional coordinations being provided by pyridine. Di-nuclear complexes were found to form urea adducts as demonstrated based on absorption and vibrational studies.© Elsevie

Four-, five- and six-coordinated Zn-II complexes of OH-containing ligands: Syntheses, structure and reactivity

Four-, five- and six-coordinated complexes of Zn-II with OH-rich molecules possessing an ONO binding core were synthesized, characterized and their structures were established by single-crystal X-ray diffraction, The corresponding metal ion geometries were found to be distorted tetrahedral, square pyramidal and octahedral, respectively. The complexes exhibit interesting lattice structures such as layered and corrugated sheets owing to the presence of a number of weak intermolecular interactions. The five-coordinated, water-bound Zn-II complex was studied because of its putative hydrolysis property towards p-nitrophenyl acetate. (C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002

Synthesis, characterisation and crystal structures of Schiff bases from the reaction of 4,6-O-ethylidene-β-D-glucopyranosylamine with substituted salicylaldehydes

Multiple chemical modifications were carried out on D-glucose to result in the corresponding Schiff bases. Such modifications performed on D-glucose not only helped in increasing the solubility of the products in nonaqueous solvents, but also restricted the anomerisation of the saccharide moiety in solution. NMR study of the products revealed the presence of the β-anomeric form of the saccharide moiety in Me2SO solution. All the compounds were characterised by analytical and spectral methods. The literature is devoid of any crystal structures of saccharide–Schiff base combinations of the type reported in this paper. The crystal structures of these molecules exhibited a tridentate, ONO binding core. These studies further revealed that the compounds in the solid state were in the β-D-pyranose form with the 4C1 chair conformation. The compounds exhibited interesting lattice structures assisted through weak interactions of the type O–H...O and C–H...O. The lattice structure of one of these compounds exhibited channels filled with chloroform molecules.© Elsevie

Structure of the first tetranuclear Ni(II) complex derived from N-(2-hydroxybenzylidene)-4,6-O-ethylidene-β-D-glucopyranosylamine

In order to understand the binding nature of the glycosylamines possessing imine functionality, a novel tetranuclear Ni(II) complex of N-(2-hydroxybenzylidene)-4,6-O-ethylidene-β-D-glucopyranosylamine having twisted Ni4O4 cubane core was synthesized and structurally characterized

Glycosylamines of 4,6-O-butylidene-α-D-glucopyranose: synthesis and characterization of glycosylamines, and the crystal structure of 4,6-O-butylidene-N-(o-chlorophenyl)-β-D-glucopyranosylamine

A total of nine glycosylamines of 4,6-O-butylidene-α-D-glucopyranose were synthesized using primary amines having various groups in their ortho- or para-positions. Among these, six are monoglycosylamines, including one primary glycosylamine, and three are bis-glycosylamines. All these compounds were characterized by 1H, 1H–1H COSY, 1H–13C COSY and 13C NMR spectroscopy and FTIR spectra. The FAB mass spectra provided the molecular weights of the products by exhibiting the corresponding molecular ion peaks. The crystal structure of 4,6-O-butylidene-N-(o-chlorophenyl)-β-D-glucopyranosylamine revealed the C-1 glycosylation, the β-anomeric nature, and the 4C1 chair conformation of the saccharide unit in the product. In the lattice two types of dimers exist. While one type of dimer is formed through O–H...O type of interactions, the other type is formed via C–H...O type of interactions. In the direction of these C–H...O type of interactions, the dimeric units are connected to form a chain.© Elsevie