Reactivity of bi- and monometallic trifluoroacetates towards amorphous SiO₂

Abstract

The reactivity of alkali–manganese(ii) and alkali trifluoroacetates towards amorphous SiO2 was studied in the solid-state with an eye towards the synthesis of alkali fluorosilicates.

Exploiting the Reactivity of Metal Trifluoroacetates to Access Alkali–Niobium(V) Oxyfluorides

“…CsNb 2 O 5 F and unreacted Nb 2 O 5 were obtained as products upon heating a CsF:Nb 2 O 5 mixture (2:3 molar ratio) in the same experimental conditions in which single-phase CsNb 3 O 7 F 2 had been prepared (Figure S8). Thus, we conclude that an intrinsic reactivity difference between CsH­(tfa) 2 and CsFperhaps due to reactive fluorinated volatiles arising from decomposition of the trifluoroacetato moieties (e.g., CF 2 ) ,− and the microenvironment within the thermogravimetric analyzer helped in achieving single-phase polycrystalline CsNb 3 O 7 F 2 .…”

“…Crystallization occurred upon solvent evaporation at 65 °C for 24 h (potassium) and 48 h (rubidium and cesium). The procedure is described in detail elsewhere . 2 mmol of metal trifluoroacetate were targeted per synthesis.…”

“…The procedure is described in detail elsewhere. 14 2 and CsH(tfa) 2 prepared via solvent evaporation and KF (99%), CsF (99.9%), and Nb 2 O 5 (99.99%) purchased from Sigma-Aldrich and used as received. Four mixtures were prepared by mixing and grinding stoichiometric amounts of the starting materials in an agate mortar in a nitrogen-filled glovebox; these were KH(tfa) 2 :Nb 2 O 5 (≈160 mg), CsH(tfa) 2 :Nb 2 O 5 (≈150 mg), KF:Nb 2 O 5 (≈100 mg), and CsF:Nb 2 O 5 (≈100 mg).…”

“…More recently, we showed that the reactivity of monometallic trifluoroacetates may be leveraged to streamline synthetic access to alkali fluorosilicates. We reported that KH­(tfa) 2 and CsH­(tfa) 2 (tfa = CF 3 COO – ) react with amorphous SiO 2 under air to yield hexa- and heptafluorosilicates K 2 SiF 6 , Cs 2 SiF 6 , K 3 SiF 7 , and Cs 3 SiF 7 . These solids are usually synthesized via solution-phase routes that entail using aqueous HF or generating HF in situ. − A distinct advantage of metal trifluoroacetates as precursors is that they serve as both metal and fluorine sources.…”

HF-Free synthesis of colloidal Cs2ZrF6 and (NH4)2ZrF6 nanocrystals

“…26 Release of gaseous oxygen-based byproducts during decomposition of M(tfa) n precursors at T ≥ 300 °C has been observed in syntheses of mono-, di-, and trivalent metal-fluorides, 27,28 and such species may interfere with formation of the target Cs 2 ZrF 6 lattice by binding to the highly oxophilic B 4+ ions. Alternatively, we do note a promising recent demonstration that solid-state thermolysis of the alkali trifluoroacetates KH(tfa) 2 and CsH(tfa) 2 will fluorinate a-SiO 2 to form crystalline K 2 SiF 6 and Cs 2 SiF 6 , 29 albeit under conditions very different from those required to form colloidal NCs.…”