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Sci. Lett. J. 2013, 2: 43
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Research Article
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Full Text
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Transition metal complexes of oxamide dioxime: Synthesis, characterization and
X-ray structure of isomorphous [Ni(H2oxado)3](BF4)2 and [Ni(H2oxado)3](ClO4)2
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Justin Nenwaa, Patrick L. Djonwouoa, Michel M. Bélombéa, Emmanuel N. Nforb, Franziska Emmerlingc
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a Inorganic Chemistry Department, Coordination Chemistry Laboratory, Faculty of Science, P.O. Box 812,
University of Yaounde 1, Yaounde, Cameroon
b Department of Chemistry, Faculty of Science, P.O. Box 63, University of Buea, Buea, Cameroon
c Bundesanstalt für Materialforschung und -prüfung, Richard-Willstätter-Str. 11, D-12489 Berlin-Adlershof, Germany
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Abstract |
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Reaction of Ni(BF4)2 or Ni(ClO4)2 with oxamide dioxime (H2oxado) in slightly acidic aqueous medium (pH ˜ 3) afforded in good yield the isomorphous salts, [Ni(H2oxado)3](BF4)2 (1) and [Ni(H2oxado)3](ClO4)2 (2), respectively. These compounds were characterized by elemental and thermal analyses, FTIR spectroscopy, and by single crystal X-ray diffraction at 273 K. The crystal packing of 1 and 2 consists of unaccustomed positively charged pillars of the chiral and paramagnetic complex cations, [Ni(H2oxado)3]2+, interlinked to one another parallel to [001] by extended one-dimensional H-bonding, with regular intra-pillar Ni...Ni spacing of 6.341(2) Å in 1 and 6.359(1) Å in 2. The positively charged pillars are disposed in the crystal framework such that Δ-[Ni(H2oxado)3]2+ counter balance Λ-[Ni(H2oxado)3]2+ enantiomers. The resulting racemic array of Δ/Λ-pillars delineates unusual co-parallel triangular channels that accommodate tightly the charge canceling anions, BF4- in 1 and ClO4- in 2. Additional transversal H-bonds, effective between the positive pillars and the anions, help to stabilize the three-dimensional bulk structures. Magnetic measurements performed on compound 2 reveal no considerable interactions within the range from room temperature down to liquid helium.
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Keywords
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Oxamide dioxime; Positive complex pillars; Triangular nanochannels; H-bonding; Crystal structure; Positive lattice framework
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