Abstract
The compounds Ba(O 2CCH 3) 2(18-crown-6)·nH 2O and Ba(O 2C(CH 2) 4CO 2)(18-crown-6)·nH 2O were prepared by the reaction between barium carbonate and the appropriate organic acid in the presence of 18-crown-6. These compounds were characterized by a variety of spectroscopic and analytical methods which showed that various hydrates could be formed. The species Ba(O 2CCH 3) 2(18-crown-6)·4H 2O( 1) and Ba(O 2C(CH 2) 4CO 2) (18-crown-6)·8H 2O ( 2) were structurally characterized by single-crystal X-ray diffraction. In the solid state compound 1 was comprised of a Ba atom in the center of the 18-crown-6 ring with chelating acetate ligands being in the axial positions of the equitorial coordination plane. Water molecules were hydrogen bonded to the oxygen atoms of the acetate ligands. Compound 2 is an infinite polymer in the solid state with the Ba atom also in the center of the 18-crown-6 ring with each carboxylate group chelating to one Ba and each adipate bridging through the second carboxylate group of the dicarboxylate to another Ba atom. Compound 1 crystallizes in the monoclinic space group P2 1/ c with cell dimensions of a = 9.512(1) A ̊ , b = 7.811(1) A ̊ , c = 16.906(1) A ̊ , ß = 99.049(8)°, V = 1240.5(3) A ̊ 3 and Z = 2 . Compound 2 crystallizes in the triclinic space group P 1 with cell dimensions of a = 8.525(1) A ̊ , b = 9.769(1) A ̊ , c = 10.200(1) A ̊ , α = 106.59(1)°, ß = 90.37(1)°, γ = 110.34(1)°, V = 757.4(1) A ̊ 3 and Z = 1 . Compounds 1 and 2 thermally decompose to evolve the 18-crown-6 ligand intact at approximately 200°C, prior to the thermal decomposition of the carboxylate ligand to form BaCO 3. Compounds 1 or 2 were mixed with Ti(O- i-Pr) 4 in ethanol, spin coated onto Pt substrates and heated to 400°C followed by annealing at 700°C for 1 h in air. Coumpound 1 resulted in formation of a mixture of BaTiO 3, BaCO 3 and TiO 2, while 2 produced only BaCO 3 films. The difference in reactivity of 1 and 2 may be connected to the availability of a thermal window for ester elimination as indicated by the TGA results.
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