Out-of-Center Distortions in d⁰ Transition Metal Oxide Fluoride Anions

Electronic effects and the bond network are the two factors that cause out-of-center distortions in octahedral d0 transition metal oxide fluoride anions. Overlap between filled oxide p orbitals and vacant cation d orbitals results in strong, short metal−oxide bonds causing the metal ion to distort toward the oxide ligand. This primary, electronic distortion is not dependent on the extended structure. Smaller, secondary distortions of the anionic octahedra are caused by interactions with the bond network. [HNC6H6OH]2[Cu(NC5H5)4(NbOF5)2], prepared with 5-hydroxy-2-methylpyridine that provides two coordination contact sites to the anion when protonated, exhibits distortions in the anion reflecting both factors. Crystal data for [HNC6H6OH]2[Cu(NC5H5)4(NbOF5)2]: monoclinic, space group C2/c (No. 15), with a = 10.9427(8) Å, b = 16.204(1) Å, c = 21.396(2) Å, β = 93.263(1)°, and Z = 4. Conditions for detection of both distortion types are discussed with five additional examples.