Chemical routes to barium-cerium oxides:: the quest for mixed-metal precursors.: Molecular structure of Ba4Ce2(μ6-O)(thd)4 (μ3-OPri)8(OPri)2

Various synthetic routes to Ba-Ce mixed-metal species have been investigated No reaction was observed between Ce-2(OPri)(8)((PrOH)-O-i)(2) (1) and barium isopropoxide. The enhanced acidity of the alcohol molecules of 1 has been used as a means to access to Ba-Ce species and to fix the stoichiometry between the metals. Ba2Ce4(OPri)(20) (2) has been obtained. This species is unstable in the presence of isopropanol giving BaCe4(OPri)(18) (3). The reaction between 1 2,2,6,6-tetramethylheptane-3,5-dione (thdH) and barium isopropoxide gives Ba4Ce2(mu(6)-O)(thd)(4)(mu(3)-OPri)(8)(OPri)(2) (4) independently of the stoichiometry used for the reac tion. The reactions between 1, barium isopropoxide and acetylacetone are more complex and different compounds, namely Ba2Ce2O(acac)(2)(OPri) (5) or BaCe2(acac)(OPri)(9) (6) are formed depending on the experimental conditions. All compounds have been characterized by elemental analysis, FT-IR, H-1 and C-13 NMR. 4 was also characterized by X-ray diffraction. Hydrolysis-polycondensation reactions have been estimated for 4 and for 6. (C) 1998 Elsevier Science Ltd. All rights reserved.