K2SnOF4 and K2WO3F2 – different but similar

K2SnOF4 and K2WO3F2 were synthesized via a high-pressure/high-temperature route. Single-crystal analysis showed that both substances crystallize in the orthorhombic crystal system with space group Pnma and are isostructural to each other. The main motifs of the structures are octahedral [SnO2F4]4− and [WO4F2]4− entities for K2SnOF4 and K2WO3F2, respectively. Within the structures, these units are connected to quasi-isolated infinite chains. The substances were further characterized via powder X-ray diffraction, EDX and FT-IR spectroscopy. Doping of K2SnOF4 with Mn4+ yielded a red phosphor material which was analyzed by luminescence spectroscopy. The emission maximum is located at λ max = 631 nm.

Synthesis of NaMoO3F and Na5W3O9F5 with Morphological Controllability in Non-Aqueous Solvents

NaMoO₃F and Na₅W₃O₉F₅ were synthesized by solvothermal reaction of MoO₃ and WO₃, respectively, with NaF in nonaqueous solvents. These reactions were realized at low temperatures (150-200 °C) without the use of HF. This synthesis method is much more facile and safe procedure compared with general synthesis methods for oxyfluorides which includes hydrothermal reaction under a presence of HF or solid-state reaction at high temperatures in vacuum sealed tube or under high pressure. In the case of the reaction of MoO₃ with NaF, the kind of solvent largely affected the obtained morphologies of NaMoO₃F. The morphology in the case of acetonitrile as a solvent was rodlike with a micrometer-scale size, while that in the case of ethanol was polyhedral with a size of several hundred nanometers. In addition, the solvothermal reaction of WO₃ with NaF led to the formation of Na₅W₃O₉F₅. Also, the difference of solvents for the solvothermal reaction affected the obtained particle sizes. The effect of the solvents on the morphologies of the obtained oxyfluorides probably resulted from the difference of the solubility of NaF and the subsequent dissolution ratio of MoO₃ or WO₃ in the used solvents. Our synthesis method can expand the applicability of oxyfluorides by providing a new phase and/or unique morphology.

Synthesis and characterization of K5Sn2OF11

The potassium oxidofluoridostannate(IV) fluoride K5Sn2OF11 was synthesized via a solid-state route at T = 300°C in arc-weldeded copper ampoules. It crystallizes in the orthorhombic system in the acentric space group Ama2 (no. 40) with a unit cell volume of V = 2.5727(4) nm3. The cell parameters are a = 1758.3(2), b = 2452.3(2) and c = 596.7(1) pm. As a main structural motif, K5Sn2OF11 exhibits two different kinds of dinuclear [Sn2OF11]5‒ units, which are embedded into a matrix consisting of potassium cations and fluoride anions. The substance was characterized by single-crystal and powder X-ray diffraction, as well as by FT-IR spectroscopy.

Chromium Oxide Tetrafluoride and Its Reactions with Xenon Hexafluoride; the [XeF5 ]+ and [Xe2 F11 ]+ Salts of the [CrVI OF5 ]- , [CrV OF5 ]2- , [CrV 2 O2 F8 ]2- , and [CrIV F6 ]2- Anions

Molten mixtures of XeF₆ and Cr^VI OF₄ react by means of F₂ elimination to form [XeF₅ ][Xe₂ F₁₁ ][Cr^V OF₅ ]⋅2 Cr^VI OF₄ , [XeF₅ ]₂ [Cr^IV F₆ ]⋅2 Cr^VI OF₄ , [Xe₂ F₁₁ ]₂ [Cr^IV F₆ ], and [XeF₅ ]₂ [Cr^V ₂ O₂ F₈ ], whereas their reactions in anhydrous hydrogen fluoride (aHF) and CFCl₃ /aHF yield [XeF₅ ]₂ [Cr^V ₂ O₂ F₈ ]⋅2 HF and [XeF₅ ]₂ [Cr^V ₂ O₂ F₈ ]⋅2 XeOF₄ . Other than [Xe₂ F₁₁ ][M^VI OF₅ ] and [XeF₅ ][M^VI ₂ O₂ F₉ ] (M=Mo or W), these salts are the only Group 6 oxyfluoro-anions known to stabilize noble-gas cations. Their reaction pathways involve redox transformations that give [XeF₅ ]⁺ and/or [Xe₂ F₁₁ ]⁺ salts of the known [Cr^V OF₅ ]^2- and [Cr^IV F₆ ]^2- anions, and the novel [Cr^V ₂ O₂ F₈ ]^2- anion. A low-temperature Raman spectroscopic study of an equimolar mixture of solid XeF₆ and CrOF₄ revealed that [Xe₂ F₁₁ ][Cr^VI OF₅ ] is formed as a reaction intermediate. The salts were structurally characterized by LT single-crystal X-ray diffraction and LT Raman spectroscopy, and provide the first structural characterizations of the [Cr^V OF₅ ]^2- and [Cr^V ₂ O₂ F₈ ]^2- anions, where [Cr^V ₂ O₂ F₈ ]^2- represents a new structural motif among the known oxyfluoro-anions of Group 6. The X-ray structures show that [XeF₅ ]⁺ and [Xe₂ F₁₁ ]⁺ form ion pairs with their respective anions by means of Xe- - -F-Cr bridges. Quantum-chemical calculations were carried out to obtain the energy-minimized, gas-phase geometries and the vibrational frequencies of the anions and their ion pairs and to aid in the assignments of their Raman spectra.