Organic compounds -- part of the class 532-570 series – Organic compounds – Heavy metal containing
Patent
1992-09-15
1993-08-17
Dees, Jose G.
Organic compounds -- part of the class 532-570 series
Organic compounds
Heavy metal containing
C07F 500
Patent
active
052370810
DESCRIPTION:
BRIEF SUMMARY
The invention relates to the preparation of indium alkoxides. More particularly, the invention allows to obtain pure indium alkoxides with a high yield, which are soluble in organic solvents and useful for coating applications, for example to form conductive transparent thin films.
Few examples of the synthesis of indium alkoxides are given in the literature. An article of J. Indian Chem. Soc, Vol LIII, Sep. 1976, pp. 867-869 entitled "A study of Indium Alkoxides In(OR).sub.3 " describes a preparation of indium tri-isopropoxide by refluxing anhydrous indium trichloride with isopropanol in the presence of sodium isopropoxide. By alcoholysis of indium tri-isopropoxide, other alkoxides can be obtained. However, indium isopropoxide and the resulting alkoxides are unlikely to be pure and contain sodium, which is not acceptable for certain applications where a high conductivity is desired; moreover, these products are not very soluble in organic solvents and are very sensitive to air, which makes them unsuitable for coating applications.
Other patents describe the synthesis of metal alkoxides consisting in reacting a metal halide with an alcohol in a basic medium.
For example U.S. Pat. No. 3,946,056 discloses a two step method to prepare stannic alkoxides. First stannic chloride is reacted with an alkylamine, preferably a dimethylamine or a trimethylamine, then the product obtained is reacted with a tertiary alcohol. The said method is not applicable to indium since the compound formed in the first step, a indium chloride/alkylamine complex is highly stable and does not further react with the alcohol.
U.S. Pat. No. 4,681,959 discloses the preparation of metal alkoxides insoluble in organic solvents, such as methoxides. In an embodiment, the preparation is a one-step process, wherein the metal halide is reacted with the alcohol in the presence of a hydrogen halide acceptor which can be an alkylamine, e.g. trimethylamine. The said hydrogen halide acceptor forms with the amine a compound soluble in reaction solvents while the alkoxide remains soluble in said solvents. Although all the examples relate to titanium alkoxides, the invention can be applied to the preparation of indium alkoxides insoluble in organic solvents. Such alkoxides are unsuitable for the preparation of coating compositions comprising organic solvents.
In the prior art, coating compositions for forming indium oxide layers were in general prepared from solutions comprising organic indium compounds; for example, the solution disclosed in U.S. Pat. No. 4,391,742 which comprises 100 parts of an indium compound and 5 to 20 parts of a stannic compound. The indium compound is an indium chelate obtained e g. by reacting indium chloride dissolved in an inert solvent with methyl acetoacetonate and n-butyl alcohol, in the presence of triethylamine.
Therefore one of the objects of the present invention is the synthesis of indium alkoxides soluble in organic solvents, which can be used in coating compositions containing such solvents. It is also desired that said alkoxides be pure, in particular that they do not contain impurities susceptible to decrease the conductivity of the final oxide layers (for example Group IA metals). Moreover, said alkoxides should be obtained with a high yield for a low cost and to be easily isolated by simple methods, e.g. crystallisation. Said alkoxides which are inherently highly moisture sensitive, should also be stabilizable to facilitate their handling.
The preparation process according to the present invention allows to obtain indium alkoxides having all the above listed properties.
The synthesis according to the present invention consists in reacting a metal halide with an alcohol in basic medium, the said synthesis allowing the preparation of indium alkoxides with a wide range of alcohols and bases.
The preparation method consists in reacting in a one-step process an indium trihalide with a mixture comprising a C.sub.3 -C.sub.20 alcohol and a strong base having a low nucleophilicity, in the presence of organic solvents, in
REFERENCES:
patent: 3641077 (1972-02-01), Rochow
patent: 3946056 (1976-03-01), Thomas
patent: 4391742 (1983-07-01), Steigerwald et al.
patent: 4681959 (1987-07-01), Ayen et al.
S. R. Bindal and R. C. Mehrotra, "A Study of Indium Alkoxides In(OR)", J. Indian Chem. Soc., vol. LIII, Sep. 1976, pp. 867-869.
Moore Christopher P.
Wettling Danielle M.
Dees Jos,e G.
Eastman Kodak Company
Legg L. George
Nazario-Gonzalez Porfirio
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