The First Fully Fluorinated Organically Templated Materials: Synthesis, Structures, and Physical Properties of [H₃N(CH₂)₃NH₃]U₂F₁₀·2H₂O, [H₃N(CH₂)₄NH₃]U₂F₁₀·3H₂O, [H₃N(CH₂)₆NH₃]U₂F₁₀·2H₂O, and [HN(CH₂CH₂NH₃)₃]U₅F₂₄

Abstract

A series of new layered uranium(IV) fluorides have been prepared under hydrothermal conditions from UO2, HF, and H3PO4 by using H2N(CH2)nNH2 (n = 3, 4, or 6), and N(CH2CH2NH2)3 as structure-directing agents. [H3N(CH2)3NH3]U2F10·2H2O (UFO-1), [H3N(CH2)4NH3]U2F10·3H2O (UFO-2), [H3N(CH2)6NH3]U2F10·2H2O (UFO-3), and [HN(CH2CH2NH3)3]U5F24 (UFO-4) have been characterized by single-crystal X-ray diffraction, thermogravimetric analysis, BET isotherms, and magnetic susceptibility measurements. UFO-1, 2, 3, and 4 contain negatively charged uranium fluoride (UF) layers constructed from linked UFn polyhedra separated by charge balancing organic cations and occluded water molecules. In UFO-1, 2, and 3, the layers are constructed from equivalent UF9 tricapped trigonal prisms that share three edges and two corners, whereas UFO-4 contains both UF8 bicapped trigonal prisms and UF9 tricapped trigonal prisms. We have demonstrated that the interlamellar organic cations in these materials can be ion-exchanged with a large variety of alkali, alkaline earth, and transition metal cations, thus providing a low-temperature route to new condensed mixed metal uranium fluorides. The magnetic susceptibility data indicate that UFO-1, 2, and 3 exhibit Curie-Wiess behavior between room temperature and 20 K. [Crystal data: UFO-1, monoclinic, space group P21/c (no. 14), a = 10.715(1) Å, b = 7.097(1) Å, c = 8.767(1) Å, β = 93.804(6)°, V = 665.21(1) Å3 (T = 150 K), Z = 2, R(F) = 5.42%, Rw(F) = 6.79%; UFO-2, triclinic, space group P1̄ (no. 2), a = 12.024(2) Å, b = 7.149(3) Å, c = 8.765(2) Å, α = 90.063(4)°, β = 107.133(5)°, γ = 92.098(3)°, V = 719.49(3) Å3 (T = 150 K), Z = 2, R(F) = 8.05%, Rw(F) = 10.11%; UFO-3, monoclinic, space group P21/c (no. 14), a = 13.800(2) Å, b = 7.056(1) Å, c = 8.720(1) Å, β = 108.338(6)°, V = 805.97(2) Å3 (T = 150 K), Z = 2, R(F) = 3.64%, Rw(F) = 4.65%; UFO-4, triclinic, space group P1̄ (no. 2), a = 11.534(2) Å, b = 11.532(4) Å, c = 9.634(2) Å, α = 104.034(4)°, β = 101.112(8)°, γ = 93.922(4)°, V = 1210.9(5) Å3 (T = 150 K), Z = 2, R(F) = 6.12%, Rw(F) = 8.19%.]