Approaches to alkaline earth metal-organic chemical vapor deposition precursors.: Synthesis and characterization of barium fluoro-β-ketoiminate complexes having appended polyether "lariats"

The synthesis and characterization of a family of beta-ketoimines derived from 1,1,1,5,5,5-hexafluoro-2,4-pentanedione (hfa) and the corresponding volatile barium beta-ketoiminate-polyether complexes having the general formula Ba[CF3COCHC(NR)CF3](2) where R = (CH2CH2O)(2)CH3, (CH2CH2O)(2)CH2CH3, and (CH2CH2O)(3)CH2CH3 is reported. These complexes can be transported in the vapor phase at 160 degrees C/0.05 Torr without decomposition. The beta-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 beta-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, beta-ketoimines, and barium complexes were characterized by elemental analysis, H-1, F-19, and C-13 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)(2)CH2CH3 [C22H28N2F12O6Ba; space group = monoclinic, P2(1); a = 12.1175(2) Angstrom, b = 14.9238(2) Angstrom, c = 16.9767(3) Angstrom, alpha = gamma = 90 degrees, beta = 90.0840(10)degrees, Z = 4] and R = (CH2CH2O)(3)CH2CH3 [C26H36N2F12O8Ba; space group = triclinic, P (1) over bar (#2); a = 10.971(2) Angstrom, b = 12.134(2) Angstrom, c = 15.280(4) Angstrom, alpha = 89.94(2)degrees, beta = 110.00(2)degrees, gamma = 116.75(2)degrees, Z = 2] were characterized by single-crystal X-ray diffraction. Both analyses reveal monomeric structures with the beta-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.