- Reactivity of mixed-metal BaCu and BaY β-diketonatoalkoxides with Lewis bases.
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Reactions involving Y(Thd)3 and Cu(thd)2 with barium tert-butoxide or 2-dimethylamino-2-propoxide were investigated. The mixed-metal complexes [YBa3(OBu1)6(thd)3] (1) and [BaCu(OBu1)2(thd)2]m (3) (thdH = 2.2.6.6-tetramethylheptane-3,5-dione) were isolated in hexane. Dissolution of 3 in Et2O or THF afforded [Cu3(OBu1)3(thd)3] (4) and [Cu(thd)2(OBu1)2(THF)2] (5), respectively, while [Ba(thd)2(TMEDA)2] (2) was obtained in the presence of N′,N′-tetramethylenediamine. Dissolution of 1 in THF afforded a THF adduct (1a) giving 1 by sublimation at 190°C 10 Torr. By contrast, the reaction between the barium aminoalkoxide and Y(thd)2 in hexane proceeded directly to the formation of homometallic compounds, whereas with Cu(thd)2 the mixed-metal compound {Ba2Cu [OCHMeCH2NMe2]2(thd)2(Pr 1OH)2} (6) was obtained by crystallization from Pr1OH. All compounds were characterized by elemental analysis. IR. 1H NMR, ESR and TGA for the copper species. Compounds 2, 4 and 6 were characterized by single-crystal X-ray diffraction. The [Ba(thd)2(TMEDA)2] adduct is monomeric. The structures of 4 and 6 consist of triangular aggregates with Cu3(μ3-OBu1)2(μ-OBu 1)(thd)3 and Ba2Cu(μ3,η2-OCHMe CH2NMe2)2(μ,η2-thd) 2(η2-thd)2(Pr1OH)2 cores, respectively. Compound 4 exhibits one square planar and two square pyramidal copper centres. The Cu-O bond lengths range from 1.90(2) to 2.27(2) A, the order of variation being Cu-O(thd) 3OR. For compound 6, the thd, OR and Pr1OH ligands are bonded asymmetrically to the three metallic centres. Each barium atom bears a chelating thd ligand, two other thd are bridging-chelating, linking the two barium atoms, and one barium, Ba(2), to the copper atom, respectively. The nitrogen-donor sites of the two μ3-aminoalkoxide ligands interact with the copper and Ba(2) centres. The two isopropanol molecules are bonded to the other barium, Ba(1): the solvate is stabilized by intramolecular hydrogen bonds. This allows the barium atoms to reach high coordination numbers, seven and eight, and the copper atom to be pentacoordinated. The Ba-O bond lengths range from 2.59(1) to 2.87(1) A. The Ba-N bond distance is 2.85(1) A. Compounds 4 and 5 are volatile; 5 loses its THF upon sublimation to yield 4.
- Labrize, Florence,Hubert-Pfalzgraf, Liliane G.,Vaissermann, Jacqueline,Knobler, Carolyn B.
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p. 577 - 589
(2008/10/08)
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- Vaporization of Barium Dipivaloylmethanate by Mass Spectrometry
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Vaporization of barium dipivaloylmethanate at 200-300°C is studied. Two temperature ranges of vaporization are distinguished: in the range 200-240°C, the condensed and gas phases are in thermodynamic equilibrium and their compositions are relatively constant; above 240°C, the processes prevail in the condensed phase such that they suppress vaporization of the melt and enrich the vapor with light molecular species. The heats of vaporization of molecular barium dipivaloylmethanate species are estimated on the basis of different suspected compositions of the saturated vapor.
- Giricheva,Isakova,Kuz'mina,Girichev,Petrov,Kaul
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p. 1457 - 1463
(2008/10/08)
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