title: catena-Poly[bis(μ-2,2'-bipyridin-6-olato)-κ³N,N':O;O:N,N'-dicopper(I,II) [[tetrafluoridoniobium(V)]-μ-oxido]].
abstract: A novel copper-niobium oxyfluoride, {[Cu₂(C₁₀H₇N₂O)₂][NbOF₄]}n, has been synthesized by a hydrothermal method and characterized by elemental analysis, EDS, IR, XPS and single-crystal X-ray diffraction. The structural unit consists of one C₂-symmetric [NbOF₄]⁻ anion and one centrosymmetric coordinated [Cu₂(obpy)₂]⁺ cation (obpy is 2,2'-bipyridin-6-olate). In the [NbOF₄]⁻ anion, each NbV metal centre is five-coordinated by four F atoms and one O atom in the first coordination shell, forming a square-pyramidal coordination geometry. These square pyramids are then further connected to each other via trans O atoms [Nb-O = 2.187 (3) Å], forming an infinite linear {[NbOF₄]⁻}n polyanion. In the coordinated [Cu₂(obpy)₂]⁺ cation, the oxidation state of each Cu site is disordered, which is confirmed by the XPS results. The disordered Cu sites are coordinated by two N atoms and one O atom from two different obpy ligands. The [NbOF₄]⁻ and [Cu₂(obpy)₂]⁺ units are assembled via weak C-H∙∙∙F hydrogen bonds, resulting in the formation of a three-dimensional supramolecular structure. π-π stacking interactions between the pyridine rings [centroid-centroid distance = 3.610 (2) Å] may further stabilize the crystal structure.
authors.affiliation: Centre of Analysis and Testing, Nanyang Normal University, Nanyang 473061, People's Republic of China.
authors.forename: Zhi-Guo
authors.initials: ZG
authors.lastname: Zhong
authors.forename: Yu-Quan
authors.initials: YQ
authors.lastname: Feng
authors.forename: Ping
authors.initials: P
authors.lastname: Zhang
keywords: coordination polymers; copper–niobium oxyfluorides; crystal structure; disordered oxidation states; heteronuclear compounds