Potassium and Rubidium Thenoyltrifluoroacetonates: Crystal-Chemical Study and Thermal Properties

Potassium, rubidium, and cesium thenoyltrifluoroacetonates (ttfac^– = C₄H₃SCOCHCOCF₃) are prepared and characterized (elemental and powder XRD, IR and NMR spectroscopy). The structure of new {K(H₂O)(ttfac)}_∞ and {Rb(ttfac)}_∞ compounds is determined by XRD (the rubidium complex is shown to be isostructural to its cesium analogue) and is shown to be layered due to M–O and M–F contacts. The presence of water in the structure diminishes the anion′s denticity. The immediate environment of K⁺, consisting of oxygen and fluorine atoms, is typical for potassium β-diketonates (coordination number = 8), whereas that of Rb⁺/Cs⁺ is an unusual coordination polyhedron with a coordination number of 7. The layers in the structures of anhydrous {M(ttfac)}_∞ are connected by C–H⋯π interactions. The structural organization of the studied complexes is compared with that of their benzoyltrifluoroacetonate analogs. Thermal properties of M(ttfac)(H₂O)_x are studied by TG-DSC with a mass spectrometric analysis of evolved gases. It is shown by powder XRD that the decomposition of potassium, rubidium, and cesium thenoyltrifluoroacetonate in air leads to the formation of corresponding sulfates as the main decomposition products.