Reactivity of mixed-metal BaCu and BaY β-diketonatoalkoxides with lewis bases: Molecular structures of [Ba 2Cu(μ 3,η 2-OCHMeCH 2NMe 2) 2(μ,η 2-thd) 2(η 2-thd) 2(Pr iOH 2], [Cu 3(μ 3-OBu t) 2(μ-OBu t)(η 2-thd) 3] and [Ba(η 2-thd) 2(TMEDA) 2

Abstract

Reactions involving Y(thd) 3 and Cu(thd) 2 with barium tert-butoxide or 2-dimethylamino-2-propoxide were investigated. The mixed-metal complexes [YBa 3(OBu t) 6(thd) 3] ( 1) and [BaCu(OBu t) 2(thd) 2] m ( 3) (thdH = 2,2,6,6-tetramethylheptane-3,5-dione) were isolated in hexane. Dissolution of 3 in Et 2O or THF afforded [Cu 3(OBu t) 6(thd) 3] ( 4) and [Cu(thd) 2(OBu t) 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 −3 Torr. By contrast, the reaction between the barium aminoalkoxide and Y(thd) 3 in hexane proceeded directly to the formation of homometallic compounds, whereas with Cu(thd) 2 the mixed-metal compound {Ba 2Cu [OCHMeCH 2NMe 2] 2(thd) 4(Pr iOH) 2} ( 6) was obtained by crystallization from Pr iOH. 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 Cu 3( μ 3-OBu t) 2( μ-OBu t)thd) 3 and Ba 2Cu( μ 3, η 2-OCHMeCH 2NMe 2) 2( μ, η 2-thd) 2( η 2-thd) 2(Pr iOH) 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) Å, the order of variation being CuO(thd) < Cu— μ-OR < Cu— μ 3-OR. For compound 6, the thd, OR and Pr iOH 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 μ 3-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) Å. The BaN bond distance is 2.85(1) Å. Compounds 4 and 5 are volatile; 5 loses its THF upon sublimation to yield 4.