Heterometal Alkoxides as Precursors in the Sol-Gel Process

Abstract

The synthesis of bimetallic alkoxides has been followed by the preparation of intriguingly stable heterometal alkoxides containing three or four different metal atoms in the same molecular species, which has led to the pos11ibility of molecularly designing a single source precursor suited to the composition of the targeted final ceramic. This has been made feasible by the extraordinary stability of the framework of heterometal alkoxides, which appears to remain intact during the initial hydrolysis reactions in the S-G process.The characterisation (by sophisticated physicochemical techniques including X-Ray crystal structure elucidation in some cases) of heterometal alkoxides appears to have added a new dimension to heterometal coordination systems which appear to be uniquely stable without the presence of metal-metal bonds or auxiliary ligands like CO, etc., enerally required for !ltabilising polymetallic S)Stems kno~n so far.

Salt-Free Synthesis of Samarium−Aluminum Mixed-Metal Alkoxides: X-ray Crystal Structures of {[(i-Pr-O)(i-Bu)Al(μ-O-i-Pr)2Sm(O-i-Pr)(HO-i-Pr)](μ-O-i-Pr)}2, [(THF)2Sm(O-t-Bu)2(μ-O-t-Bu)2Al(i-Bu)2], Sm(OAr)3(THF)3 (Ar = 2,4,6-Me3C6H2), [Nd(μ-OAr)(OAr)2(py)2]2 (Ar = 2,4,6-Me3CGiesbrecht1, Gordon2, Clark3 et al. 2002Inorg. Chem.265150View full textAdd to dashboardCite

“…In recent years, the preparation of metal alkoxide complexes for use in the sol−gel synthesis of metal oxide materials has become an area of considerable research interest. − In addition to its utility in the preparation of metal oxide phases containing a single metal, the sol−gel process has also been utilized to prepare mixed-metal oxides, either by sol−gel processing of a mixture of two metal alkoxides in the desired stoichiometric ratio, or by processing of a single-source mixed-metal alkoxide. − The synthesis of mixed-metal lanthanide−aluminum alkoxides as precursors to lanthanide-doped alumina appears to be an attractive area for study. Current applications of lanthanide-doped alumina include preparing phosphors for display panels, synthesizing doped ceramic materials, and increasing the catalytic activity of alumina-supported platinum catalysts, while lanthanide-doped aluminum phosphate films are currently under study for their applicability in optical devices. , Previously described examples of mixed-metal lanthanide−aluminum alkoxides include the lanthanide(II) complexes Ln[Al 3 (O- i -Pr) 11 ] (Ln = Sm, Yb) and the lanthanide(III) species Ln[Al(O- i -Pr) 4 ] 3 (Ln = Y, La, Pr, Nd, Sm, Dy, Yb), Er[Al(O- i -Pr) 4 ] 3 , and {Pr[Al(O- i -Pr) 4 ] 2 (Pr- i -OH)(μ-Cl)} 2…”