The synthesis and characterization of a family of β-ketoimines derived from 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hfa) and the corresponding volatile barium β-keioiminate - polyether complexes having the general formula Ba[CF3COCHC(NR)CF3]2 where R = (CH2CH2O)2CH3, (CH2CH2O)2CH2CH3, and (CH2CH2O)3CH2CH3 is reported. These complexes can be transported in the vapor phase at 160 °C/0.05 Torr without decomposition. The β-ketoiminate ligands are synthesized by condensation of the appropriate amine-terminated poly(ethylene oxide)s with the trimethylsilyl enol ether derivative of hfa and converted to barium β-ketoiminate - polyether complexes by reaction with BaH2. The poly(ethylene oxide) amines are in turn synthesized by triphenylphosphine-mediated reduction of the corresponding poly(ethylene oxide) azides (synthesized via the tosylates) to afford the amines in good yields and analytical purity. The amines, β-ketoimines, and barium complexes were characterized by elemental analysis, 1H, 19F, and 13C NMR spectroscopy, mass spectroscopy, and thermogravimetric analysis. The eight-and ten-coordinate Ba2+ complexes having the formula Ba[CF3COCHC(NR)CF3]2 where R = (CH2CH2O)2CH2CH3 [C22H28N2F12O6Ba; space group = monoclinic, P21; a = 12.1175(2) Å, b = 14.9238(2) Å, c = 16.9767(3) Å, a = γ = 90°, β = 90.0840(10)°, Z = 4] and R = (CH2CH2O)3CH2CH3 [C26H36N2F12O8Ba; space group = triclinic, P1 (#2); a = 10.971(2) Å, b = 12.134(2) Å, c = 15.280(4) Å. α = 89.94(2)°, β = 110.00(2)°, γ = 116.75(2)°, Z=2] were characterized by single-crystal X-ray diffraction. Both analyses reveal monomeric structures with the β-ketoiminate ligands coordinated to the Ba2+ center through all available oxygen and nitrogen atoms. These complexes are substantially more volatile than Ba(2,2,6,6,-tetramethyl-3,5-heptanedionate)2 but less so than the most volatile Ba(1,1,1,5,5,5-hexafluoro-2,4-pentanedionate)2·polyether complexes.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry