Bimetallic Trifluoroacetates as Precursors to Layered Perovskites AMnF (A = K, Rb, and Cs).

Four novel alkali-manganese(II) trifluoroacetates were synthesized, and their potential as self-fluorinating precursors to layered perovskites AMnF (A = K, Rb, and Cs) was demonstrated. NaMn(tfa), KMn(tfa), RbMn(tfa)·0.23HO, and CsMn(tfa)(tfaH) (tfa = CFCOO and tfaH = CFCOOH) were grown as single crystals, and their crystal structures solved using X-ray diffraction. Chemically pure KMn(tfa), RbMn(tfa)·0.23HO, and CsMn(tfa)(tfaH) were also prepared in polycrystalline form as confirmed by thermal analysis and powder X-ray diffraction. Thermolysis of these powders yielded the isostructural series KMnF, RbMnF, and CsMnF at low temperatures (≈200-300 °C). Trifluoromethyl groups belonging to the trifluoroacetato ligands served as the fluorine source, thereby eliminating the need for external fluorinating agents. KMnF and RbMnF were obtained as single-phase powders, whereas CsMnF crystallized along with CsMnF. Access to polycrystalline CsMnF coupled to Rietveld analysis enabled elucidation of the crystal structure of this ternary fluoride, which had remained elusive. Findings presented in this article expand the synthetic accessibility of polycrystalline AMnF fluorides, for which a scarce number of routes is available in the literature.