Crown-templated assembling of the inorganic binuclear fluoro-containing anions in the system ZrO 2/HfO 2 (Nb 2O 5/Ta 2O 5)–HF–H 2O-azacrown ether

Abstract

The interaction of ZrO 2/HfO 2 or Nb 2O 5/Ta 2O 5 with an aqueous solution of hydrofluoric acid in the presence of aza-crown ether resulted in novel organically templated metal oxyfluorides of the compositions [(HA15C5) 2][Ta 2F 10O] ( 1), [(HA18C6 · H 2O)(A18C6 · H 2O)][(H 2O)Nb 2F 9O] · H 2O ( 2), [(HA18C6 · H 2O)(M 2F 10 · 2H 2O) · (H 3O) · H 2O] ( 3, 4) and [(H 2DA18C6)(M 2F 10 · 2H 2O) · 2H 2O] ( 5, 6) (M = Zr, Hf, A15C5 = aza-15-crown-5, A18C6 = aza-18-crown-6, DA18C6 = diaza-18-crown-6). Complexes 1– 6 were identified by single crystal X-ray diffraction. In 1, the negative charge of the [(TaF 5) 2O] 2− centrosymmetric dianion is balanced by two azonia-15C5 cations, while in 2 the charge of asymmetric [(H 2O)NbF 4ONbF 5] − monoanion is compensated by azonia-18C6 cation. The crystal of 2 revealed an extensive hydrogen bonding between the anions, protonated and neutral macrocycles and water molecules that combine the components into 2D sheet. Complexes 3– 4 and 5– 6 are isostructural in pairs; in all of them the rigid 2D inorganic motif is formed through the association of the [(M 2F 10 · 2H 2O)] 2− anions by means of OH⋯F hydrogen bonds. The similar 3D supramolecular architecture in 3– 6 represents an alternation of the negatively-charged inorganic sheets and the columns of (HA18C6) + or (DA18C6) 2+ organic cations glued by oxonium cations or water molecules.