Synthesis, Characterization, and Thermal Behavior of Polydentate Ligand Adducts of Barium Trifluoroacetate

Abstract

The reaction of BaH2 with polydentate ligands and CF3COOH in THF at −40 °C in 1:1:2 stoichiometries leads to compounds of general formula [Ba(O2CCF3)2]mLn (L = 12-crown-4 (1), triglyme (2), 2-(hydroxymethyl)-15-crown-5 (15-crown-5CH2OH) (3), cryptand(222) (4), 18-crown-6·C5H5N (5), 2-(hydroxymethyl)-18-crown-6 (18-crown-6CH2OH) (6)). A sulfonate compound, Ba(O3SCF3)2(tetraglyme) (7), was also prepared by a similar reaction. The polydentate ligands of 1−6 are coordinated to the barium atoms through all of their donating atoms, and the trifluoroacetate ligands are found in four distinct types of bonding modes. The compounds were characterized by spectroscopic and analytical methods, and 1−6 are among the first examples of group 2 trifluoroacetate compounds with mononuclear or dinuclear structures in the solid state as determined by single-crystal X-ray diffraction. Ba2(O2CCF3)4(12-crown-4)2 (1) crystallizes from ethanol in monoclinic space group P21/n with a = 11.014(1) Å, b = 12.016(1) Å, c = 15.269(1) Å, β = 104.47(1)°, and Z = 4. Ba2(O2CCF3)4(triglyme)2 (2) crystallizes from ethanol in monoclinic space group P21/n with a = 11.203(1) Å, b = 12.220(1) Å, c = 15.451(1) Å, β = 107.61(1)°, and Z = 4. Ba2(O2CCF3)4(15-crown-5CH2OH)2 (3) crystallizes from ethanol in monoclinic space group P21/c with a = 12.445(2) Å, b = 12.499(3) Å, c = 15.615(2) Å, β = 111.11 (1)°, and Z = 4. Ba(O2CCF3)2(cryptand(222)) (4) crystallizes from toluene in the tetragonal space group P43212 with a = b = 9.263(2) Å, c = 35.897(7) Å, and Z = 4. Ba(O2CCF3)2(18-crown-6)(py) (5) crystallizes from pyridine in orthorhombic space group Pnma with a = 27.178(3) Å, b = 11.417(1) Å, c = 9.133(1) Å, and Z = 4. Ba(O2CCF3)2(18-crown-6CH2OH) (6) crystallizes from ethanol in monoclinic space group Pn with a = 8.279(1) Å, b = 11.410(1) Å, c = 13.661(2) Å, β = 98.41(1)°, and Z = 2. Infrared spectroscopy on 1−6 supplied information on the relationships among νasym(CO2), bonding mode of the trifluoroacetate ligand, and donating ability of the polydentate ligand. Thermogravimetric analysis of 1−7 shows loss of the organic supporting ligands in the temperature range 250−600 °C with formation of BaF2.