Synthetic and Structural Studies Bismuth/Copper Alkoxides
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SYNTHETIC AND STRUCTURAL STUDIES OF BISMUTH/COPPER ALKOXIDES
WILLIAM J. EVANS* AND JOHN H. HAIN, JR. Department of Chemistry, University of California-Irvine, Irvine, California 92717 ABSTRACT The reaction of Bi[OC(CH 3 )3 ] 3 with [Cu(9-O2CCH3)212 has been investigated as a possible route to mixed-metal materials containing bismuth and copper. The product distribution obtained from this reaction depends not only upon the stoichiometry, but also upon the method of product isolation. Products containing bismuth and copper are obtainable as well as an unusual, soluble hexametallic copper(Hi) alkoxide acetate complex, Cu 6 [OC(CH 3 )316 (0 2 CCH 3 )6 . The mixed-metal products were examined by differential scanning calorimetry, and thermolyzed and hydrolyzed samples of these products were compared by scanning electron microscopy. INTRODUCTION The recent discovery that mixed-metal oxides such as YBa2Cu307-x [1], Bi2Sr2Ca2Cu3010 [2] and TlBa2Ca3Cu4O11 [3] are superconducting at temperatures above 90 K has stimulated research on the preparation of high purity samples of these materials [4,5]. Hydrolysis of heteropolymetallic alkoxides via sol-gel processes offers one route to high purity oxides [6,7], but utilization of this approach is hindered by insufficient synthetic and structural information on mixed-metal alkoxide precursors. In fact, only limited data are available even on single metal alkoxide precursors. For example, we only recently obtained the first X-ray crystallographic data on bismuth alkoxides, Bi(OR) 3 (R = C(CH 3 )3 and C6 H 4 (CH 3 )2-2,6) [8]. These data showed that these bismuth alkoxides are monomeric in the solid-state and that Bi(OC 6 H 4 Me 22,6)3 has a pyramidal structure presumably due to a stereochemically active lone pair of electrons on bismuth. We have now investigated the utility of these bismuth complexes for the preparation of mixed-metal compounds containing copper. We describe here our results using the bimetallic copper(II) complex [Cu(i-0 2CCH 3 )2] 2. EXPERIMENTAL Bi(OCMe 3 )3 , prepared as previously described [81, and commercially available anhydrous [Cu(O 2 CMe) 2 12 (Alfa) were reacted in the stoichiometries described in the following sections in THF dried over sodium benzophenone ketyl in an inert atmosphere glove box.
Mat. Res. Soc. Symp. Proc. Vol. 180. 01990 Materials Research Society
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The 1:1 [Cu2(O2CMe)2]2:Bi(OCMe3•3 Reaction Bi(OCMe3)3 (0.729 mmol) was added to a blue, stirred solution of [Cu(O2CMe)2]2 (0.729 mmol) in 20 mL of THF. The solution immediately became forest green. After 6 hours, THF was removed by rotary evaporation to leave a green solid. The solid was extracted with hexane to form a bluegreen solution, A, which was separated from the remaining blue solid, B, by centrifugation. Removal of hexane from solution A left a solid which contained primarily Cu6(O2CMe)6(OCMe3)6, 1, (46% yield based on copper) with a small amount of a bismuth contaminant present. Recrystallization from THF/hexane at-34°C generated pure Cu6(,-OCMe3)6(•-O2CMe)4(,4O2CMe)2, isolat
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