Abstract
The reactivity of alkali-manganese(II) and alkali trifluoroacetates towards amorphous SiO(2) (a-SiO(2)) was studied in the solid-state. K(4)Mn(2)(tfa)(8), Cs(3)Mn(2)(tfa)(7)(tfaH), KH(tfa)(2), and CsH(tfa)(2) (tfa = CF(3)COO(-)) were thermally decomposed under vacuum in fused quartz tubes. Three new bimetallic fluorotrifluoroacetates of formulas K(4)Mn(3)(tfa)(9)F, Cs(4)Mn(3)(tfa)(9)F, and K(2)Mn(tfa)(3)F were discovered upon thermolysis at 175 °C. K(4)Mn(3)(tfa)(9)F and Cs(4)Mn(3)(tfa)(9)F feature a triangular-bridged metal cluster of formula [Mn(3)(μ(3)-F)(μ(2)-tfa)(6)(tfa)(3)](4-). In the case of K(2)Mn(tfa)(3)F, fluoride serves as an inverse coordination center for the tetrahedral metal cluster K(2)Mn(2)(μ(4)-F). Fluorotrifluoroacetates may be regarded as intermediates in the transformation of bimetallic trifluoroacetates to fluoroperovskites KMnF(3), CsMnF(3), and Cs(2)MnF(4), which crystallized between 250 and 600 °C. Decomposition of these trifluoroacetates also yielded alkali hexafluorosilicates K(2)SiF(6) and Cs(2)SiF(6) as a result of the fluorination of fused quartz. The ability to fluorinate fused quartz was observed for monometallic alkali trifluoroacetates as well. Hexafluorosilicates and heptafluorosilicates K(3)SiF(7) and Cs(3)SiF(7) were obtained upon thermolysis of KH(tfa)(2) and CsH(tfa)(2) between 200 and 400 °C. This ability was exploited to synthesize fluorosilicates under air by simply reacting alkali trifluoroacetates with a-SiO(2) powder.