Potassium and Rubidium Benzoyltrifluoroacetonates: A Crystal Chemical Study and Thermal Properties

Abstract

Complexes of potassium and rubidium with benzoyltrifluoroacetone (C6H5COCH2COCF3 = Hbtfac) of the composition M(btfac)(H2O)x, where M = K, Rb, x ∈ [0.5 … 1] are synthesized for the first time. The compounds are characterized by the elemental analysis and IR spectroscopy. By X-ray crystallography the crystal structures of M(btfac)(H2O) are determined: for the potassium complex a = 10.4955(4) A, b = 13.9715(6) A, c = 7.5197(3) A, α = β = γ = 90°, space group Pcc2, Z = 4, R = 0.0242 [I > 2σ(I)]; for the rubidium complex a = 10.6363(8) A, b = 27.9354(18) A, c = 7.7205(5) A, α = 90°, β = 93.759(2)°, γ = 90°, space group P21/c, Z = 4, R = 0.0287. The compounds represent layered coordination polymers where the metal cation coordinates eight oxygen atoms of four β-diketonate anions or four fluorine atoms of four β-diketonate ligands and four oxygen atoms of water molecules. The structures of M(btfac)(H2O) complexes with M = K, Rb, Cs are compared and the common structural motifs are revealed. From the thermogravimetry data the melting points and temperature ranges of the stability of anhydrous complexes are found.