SYNTHESIS AND STRUCTURES OF VOLATILE MONONUCLEAR AND PENTANUCLEAR CHELATES OF BARIUM

The structures of two Ba(II) chelates of beta-diketonates have been determined; one is mononuclear and the other is multinuclear. The Ba(II) chelate of the anion of 2,2,6,6-tetramethyl-3,5-heptanedione (thd) recrystallized from pentane formed monoclinic crystals, space group I2/a. with dimensions a =24.365(9) angstrom, b =21.174(10) angstrom, c = 48.486(16) angstrom, beta = 100.98(3)degrees, and Z = 8. This structure was determined to be a beta-diketonate deficient pentanuclear complex with the formula Ba5(thd)9(H2O)3(OH). Both beta-diketonate and water ligands act as bridges between barium ions in this structure, resulting in a thermally unstable compound. A new mononuclear anionic Ba(II) chelate of 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate (hfa) has been synthesized. X-ray diffraction analysis of the monoclinic (space group C2/c) crystals gave a unit cell of dimensions a = 22.379(7) angstrom, b = 12.143(3) angstrom, c = 34.800(8) angstrom, beta = 102.22(2)degrees, and Z = 8; its structure was determined to be (ethylenediamine-H-2)1.5[Ba(hfa)5].C2H5OH. The thermal properties of (enH2)1.5[Ba(hfa)5].C2H5OH were investigated by thermogravimetric analysis. It was determined that this mononuclear anionic complex is volatile and thermally stable when compared to previously reported Ba(II) beta-diketonate complexes.