title: Synthesis, characterization and crystal structure of the new pentahydrate of bis(2,2'-bipyridine-κ(2)N,N')(oxalato-κ(2)O(1),O(2))nickel(II).
abstract: The reaction of NiCl2, K2C2O4·H2O and 2,2'-bipyridine (bpy) in water-ethanol solution at 281 K yields light-purple needles of the new pentahydrate of bis(2,2'-bipyridine)oxalatonickel(II), [Ni(C2O4)(C10H8N2)2]·5H2O or [Ni(ox)(bpy)2]·5H2O, while at room temperature, deep-pink prisms of the previously reported tetrahydrate [Ni(ox)(bpy)2]·4H2O [Román, Luque, Guzmán-Miralles & Beitia (1995), Polyhedron, 14, 2863-2869] were gathered. The asymmetric unit in the crystal structure of the new pentahydrate incorporates the discrete molecular complex [Ni(ox)(bpy)2] and five solvent water molecules. Within the complex molecule, all three ligands are bonded as chelates. The complex molecules are involved in an extended system of hydrogen bonds with the solvent water molecules. Additionally, π-π interactions also contribute to the stabilization of the extended structure. The dehydration of the pentahydrate starts at 323 K and proceeds in at least two steps as determined by thermal analysis.
authors.affiliation: Department of Inorganic Chemistry, Faculty of Sciences, P. J. Šafárik University in Košice, Moyzesova 11, 041 54 Košice, Slovakia.
authors.forename: Nela
authors.initials: N
authors.lastname: Farkašová
authors.affiliation: Department of Inorganic Chemistry, Faculty of Sciences, P. J. Šafárik University in Košice, Moyzesova 11, 041 54 Košice, Slovakia.
authors.forename: Juraj
authors.initials: J
authors.lastname: Cernák
authors.affiliation: Instituto de Sintesis Química y Catálisis Homogénea (ISQCH), Departamento de Química Inorgánica, CSIC-University of Zaragoza, Pedro Cerbuna 12, E-50009 Zaragoza, Spain.
authors.forename: Milagros
authors.initials: M
authors.lastname: Tomás
authors.affiliation: Instituto de Ciencia de Materiales de Aragón (ICMA), Departamento de Química Inorgánica, CSIC-University of Zaragoza, Pedro Cerbuna 12, E-50009 Zaragoza, Spain.
authors.forename: Larry R
authors.initials: LR
authors.lastname: Falvello
keywords: IR spectra; TGA/DTA analysis; bis(2,2′-bipyridine)(oxalato)nickel(II); crystal structure; hydrogen bonding; pentahydrate; π–π interactions