title: Crystal structures of two nickel compounds comprising neutral NiIIhydrazone complexes and di-carb-oxy-lic acids.
abstract: Two isostructural NiIIcompounds, bis-{N-[1-(pyridin-2-yl-κN)eth-ylidene]pyridine-4-carbohydrazonato-κ2N',O}nickel(II)-2,5-di-chloro-terephthalic acid (1/1), [Ni(C13H11N4O)2](C8H4Cl2O4), and bis-{N-[1-(pyridin-2-yl-κN)eth-ylidene]pyridine-4-carbohydrazonato-κ2N',O}nickel(II)-2,5-di-bromo-terephthalic acid (1/1), [Ni(C13H11N4O)2](C8H4Br2O4), were synthesized and their crystal structures determined. The pair ofN,N',O-tridentateN-[1-(pyridin-2-yl-κN)eth-yl]pyridine-4-carbohydrazonateLligands result in acis-NiO2N4octa-hedral coordination sphere for the metal ions. The asymmetric units consist of two half-mol-ecules of the di-carb-oxy-lic acids, which are completed by crystallographic inversion symmetry. In the respective crystals, the 2,5-di-chloro-terephthalic acid (H2Cl2TPA,1-Cl) mol-ecules form zigzag hydrogen-bonded chains with the [Ni(L)2] mol-ecules, with the hydrogen-bond distances in1-Brslightly longer than those in1-Cl. The packing is consolidated by aromatic π-π stacking between the di-carb-oxy-lic acid mol-ecules and terminal pyridine rings in [Ni(L)2] and short halogen-halogen inter-actions are also observed. The qualitative prediction of the H-atom position from the C-N-C angles of the terminal pyridine rings inLand the C-O distances in the carboxyl groups show that1-Cland1-Brare co-crystals rather than salts.
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motoka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Takumi
authors.initials: T
authors.lastname: Nakanishi
authors.affiliation: Institute for Materials Chemistry and Engineering, Kyushu University, 744 Motoka, Nishi-ku, Fukuoka 819-0395, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Sato
keywords: co-crystal; crystal structure; di­carb­oxy­lic acid; halogen–halogen inter­actions; hydrazone complex; hydrogen bond