Organically Templated Zirconium Fluorides: Hydrothermal Syntheses, Structural Relationships, and Thermal Behavior of (C2H10N2)Zr2F10·H2O and (C4H12N2)ZrF6·H2O

Abstract

The organically templated Zr(IV) fluorides, (C2H10N2) Zr2F10·H2O (AU2-6) and (C4H12N2)ZrF6·H2O (AU1-6) have been prepared from the reaction of ZrO2 with HF and ethylenediamine or piperazine under mild hydrothermal conditions. These compounds were characterized by single-crystal X-ray diffraction, DSC, TGA, and elemental analysis. AU2-6 consists of dodecahedral ZrF8 units that share three edges with neighboring dodecahedra to form 2∞[Zr2F10]2− sheets that are separated by diprotonated ethylenediamine cations. AU1-6 contains edge-sharing ZrF8 dodecahedra that form 1∞[ZrF6]2− chains that further hydrogen bond with diprotonated piperazinium cations and water molecules. Application of dimensional reduction theory demonstrates that 1∞[ZrF6]2− chains can be derived from the 2∞[Zr2F10]2− parent structure through the addition of one equivalent of fluoride. Thermal analyses indicate that the water molecules in AU2-6 are more tightly bound than those in AU1-6 as endotherms corresponding to water loss occur at 226 and 117°C in AU2-6 and AU1-6, respectively. Crystallographic data: AU2-6, monoclinic, space group P21/n, a=6.164(1), b=15.612(3), c=11.227(2) Å, β=95.31(3)°, Z=4, MoKα, λ·0.71073, R(F)=2.94% for 155 parameters with 3294 reflections with I>2σ(I); AU1-6, monoclinic, space group C2/m, a=12.190(5), b=12.732(6), c=6.356(2) Å, β=107.64(3)°, Z=4, MoKα, λ=0.71073, R(F)=1.68% for 77 parameters with 869 reflections with I>2σ(I).