BARIUM BETA-KETOIMINATE COMPLEXES CONTAINING APPENDED ETHER LARIATS - SYNTHESIS, CHARACTERIZATION, AND IMPLEMENTATION AS FLUORINE-FREE BARIUM MOCVD PRECURSORS

The synthesis and characterization of six volatile fluorine-free barium coordination complexes based upon encapsulating beta-ketoiminate ether/polyether ligation and having the general formula Ba(RCOCHC(NR')R'')2 (R = tert-butyl; R'= CH2CH2OCH3, -(CH2CH2O-)2CH3, -(CH2CH2O)3CH2CH3; and R'' = methyl or tert-butyl) is reported. The complexes were prepared by a nonaqueous approach which employs BaH2 and the corresponding beta-ketoimine. These complexes have been characterized by H-1 and C-13 NMR spectroscopy, elemental analysis, mass spectroscopy, cryoscopy, and thermogravimetric analysis. Single-crystal X-ray structural analysis of bis-2,2-dimethyl-5-N-(2-(2-methoxy)ethoxyethylimino)-3-hexanon ato]barium(II) reveals a monomeric eight-coordinate, distorted dodecahedral configuration about barium: space group = C2/c; a = 32.764(6) angstrom, b = 12.110(2) angstrom, c = 15.690(5) angstrom, beta = 102.12(2), Z = 8; R(F) = 0.044, R(W)(F) = 0.040 for 2776 reflections having I > 3sigma(I). Single-crystal X-ray structural analysis of bis[2,2-dimethyl-5-N-(2-(2-(2-ethoxy)ethoxy)ethoxyethylimino)-3-hexanonato]barium(II) also reveals a monomeric eight-coordinate distorted dodecahedral configuration about barium: space group = Pccn; a = 24.939(4) angstrom, b = 10.546(2) angstrom, c = 14.349(4) angstrom, Z = 4; R(F) = 0.036; R(W)(F) = 0.035 for 1689 reflections having I > 3sigma (I). Single-crystal X-ray structural analysis of bis[ 5-N-(2-methoxyethylimino)-2,2,6,6-tetramethyl-3-heptanonato]ba rium(II) indicates a nearly symmetric Ba2(mu2-O-ketoiminate)2 dimeric structure. Each half of the dimer possesses a distorted pentagonal pyramidal local configuration about the barium ion with an unusual O, O coordination of one of the ketoiminate rings: space group = C2/c; a = 27.687(5) angstrom, b = 10.453(2) angstrom, c = 22.679(6) angstrom, beta = 101.88(2), Z = 8; R(F) = 0.033, R(W)(F) = 0.042 for 4881 reflections having I > 3sigma(I). These complexes are volatile and can be used as MOCVD precursors. Thus, BaPbO3 films have been grown using these complexes and Pb(dipivaloylmethanate)2 and have been characterized by X-ray diffraction, scanning electron microscopy energy-dispersive X-ray spectroscopy, and variable-temperature resistivity measurements. Thermolytic decomposition of the barium beta-ketoiminate complexes involves cleavage of the C-O bond beta to nitrogen and affords pinacolone, 2,2-dimethyl-5-imino-3-hexanone, and 2-methyl-4-tert-butylpyridine as the major organic thermolysis products.