CA2002606A1 - Organic solvent soluble superconductor metal precursor alkoxides - Google Patents

Abstract

ORGANIC SOLVENT SOLUBLE SUPERCONDUCTOR
METAL PRECURSOR ALKOXIDES

ABSTRACT OF THE DISCLOSURE

Organic solvent soluble superconductor metal precursor alkoxides, which are essentially free of alkali and halogen contamination, can be formed by reaction of the desired metal with an alkoxy alkanol, preferably with activation of the metal towards the reaction.

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Description

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ORGANIC SOLVENT SOLUB~E SUPERCONDUCTOR
METAL PRECURSOR ALKOXIDES

RACKGROUND OF THE PRESENT INVENTION

The present invention relates to superconductor metal precursor alkoxides which are essentially alkali-free and halogen-free, and to organic solutions containing them.
There is currently much research work being done in regard to high Tc metal oxide superconductors. The instant invention relates to a particular class of metal alkoxides which are soluble in organic solvent which can be used to make such superconductors by appropriate hydrolysis of the alkoxide and firing of the resulting metal oxide which is in the form of a gel initially. The metal component in the alkoxide is one of the metals which forms an important part of the superconductor. Examples of such metals include copper, yttrium, barium, bismuth, erbium, europium, neodymium, terbium, gadolinium, lanthanum, and the like.
The term "superconductor metal precursor" as used herein is intended to refer to such metal portion of the "alkoxide"
which will eventually form the metal portion of the desired high Tc metal oxide superconductor. It is an important feature of the instant alkoxides that they are free of alkali contamination ("alkali" being intended to connote the "alkali metals" of Group IA of the Periodic Table, as well as those "alkaline earth metals" of Group IIA) and halide contamination (e.g., of chloride or bromide)0 The presence of alkali and/or halide contamination in the final metal oxide superconductor would have extremely deleterious effect upon the desired performance of the superconductor.
U.S. Patent No. 3,277,002 mentions the formation of certain alcohol soluble me~al alkoxides but utilizes a procedure in which an alkali metal alkoxide (e.g., sodium ~1;)2g~

alkoxide~ is reacted with a metal salt (i.e., MXn) to form the desirad alkoxide. soth the alkoxide and any solvent containing it would be contaminated to an unacceptable degree with either, or both, of the alkali and halide moieties forming the metal salt. Example 3 in that patent mentions 0.1% chloride contamination, and Example 4 mentions a measurable chloride contamination level of less than 0.1%
chloride. These levels are unacceptably high for the fabrication of metal oxide superconductors.
U.S. Patent No. 3,488,303, which relates to the stabilization of oxymethylene polymers wherein either a lanthanide metal salt of a non-nitrogenous alcohol or a lanthanide metal salt of a non-nitrogenous organic acid can be used as the stabilizing additive. Despite a vague disclosure at Col. 8, lines 7-12 that certain alcohol-ethers can be used to form the former class of salt, no disclosure is presented as to how such compounds might be formed or how they might differ in properties from analogous salts formed from saturated monohydric alcohols such as ethanol, and the like.
European Patent Publications No. 244,916 and 244,917 describe certain organic solvent soluble alkoxides of such metals as calcium, strontium, barium, scandium, yttrium, lanthanum and zinc which contain ligands derived from alkoxy alcohols.

SUMMARY QF THE PRE~ENT INVENTION
The present invention relates to organic solvent soluble superconductor metal precursor alkoxides, which are essentially frse of alkali and halogen contamination, and which contain ligands derived from alkoxy alkanols. The invention also comprises organic solvents containing such alkoxides.

DETAILED DESCRIPTION OF THE PRESENT INVENTION
As earlier mentioned, the term "superconductor metal precursor" is intended to connote those metals which form the metal moieties in the high Tc superconductor metal oxides that are currently of interest to research and industry. Representative metals of this type can be found in the following Groups of the Periodic Table (as depicted on page 662 of The Condensed Chemical Dictionary, ninth Edition): IIA ~calcium, strontium and barium); IIIB
(scandium, yttrium, and lanthanum (including the rare earth metals); IB (copper); and VA (bismuth).
Th~ alkoxy ligand -OR attached to such a metal in the alkoxide is derived from an alkoxy alcohol of the formula ROH where R is -R'OR" with the sum total of carbon atoms in R' and R" being from about 3 to about 8 with Rl' being Cl~C4.
Representative alkoxy alkanols are methoxypropanol, methoxybutanol, methoxyethanol and butoxyethanol.
The organic solvent soluble superconductor metal precursor alkoxides of the instant invention can be synthesized by reacting the above-described desired metal with the alkoxy alkanol. A suitable catalyst (e.g., mercuric chloride) may be necessary to achieve acceptable yields as shown in Exa~ples 7-11. Since certain of the metal moieties selected are relatively unreactive, it may be necessary to activate them towards the desired reaction.
This can be accomplished by grinding the metal as described in U.S. Patent No. 4,670,573 of C. C. Greco or by using ultrasonic vibrations to activate the metal as described in co-pending application entitled "Activated Metal Alkoxide Synthesis", filed on even date herewith.

An alternative synthesis route involves an alcohol exchange reaction of the metal alkoxide (e.g., the m~thoxide) with the desired alkoxy alkanol as shown in Examples 1-2, 4 and 6, herein.
The instan~ invention is further illustrated by the Examples which ~ollow.

AST 5439 _5_ 6G~;

Copper methoxide (5 millimoles) was suspended in lo mL of toluene, and 10 mL of 3-methoxy-1-butanol was added.
The reaction mixture was warmed to 120C, and it was sparged with nitrogen to remove methanol formed in the resulting alcohol exchange reaction. Then, a solution of di(2-methoxy-l-propoxy) barium was added (10.4 grams o~ solution containing 4.4 weight % barium). Nitrogen sparging was continued for five more minutes, and the reaction mixture was cooled to room temperature. A solution of tri(3-methoxy-l-butoxy) erbium (3.3 grams containing 8~5 weight %
of Er) was then added. The homogeneous sample was then stored for a period of 30 days. No visible sign of decomposition was observed.

Copper methoxide (5 m~llimoles) was suspended in 10 mL of toluene, and 10 mL of 3-methoxy-1-butanol was added.
The reaction mixture was warmed to 120C, and it was sparged with nitrogen to remove methanol formed in the resulting alcohol exchange reaction. Then, a solution of di(2-methoxy-l-propoxy) barium was added (10.4 grams of solution containing 4.4 weight % barium). Nitrogen sparging was continued for five more minutes, and the reaction mixture was cooled to room temperature. A solution of tri(3-methoxy-l-butoxy) europium (3.5 mL containing 7.3 weight of Eu) was then added. The homogeneous sample was then stored for a period of 15 days. No visible sign of decomposition was observed.

2~

EX~MPLE 3 Bismuth methoxide was prepared according to slightly modified literature procedure (R. C. Mehrotra and A. K. Rai, Indian J. Chem. 4 (12), 537), starting with 25 grams of anhydrous bismuth trichloride, 1.84 grams of lithium, and 200 mL of methanol.

Bismuth methoxide from Example 3 was suspended in ~00 mL of toluene and 100 mL of 3-methoxy-1-butanol. The reaction mixture was placed in an oil bath at 128C, and the suspension was sparged with nitrogen for a period of forty-five minutes. Trimethylbenzene (100 mL) was then added, and the material was filtered. The final concentration of the product was 4.0 weight ~ of bismuth. The amount of recovered solution was 123.4 grams.

AST 5439 _7_ 21~0~

To a solution of copper/barium 3-methoxy-1-butoxide (17.97 grams) containing 3.75 weight % barium and 2.66 weight % copper in a toluene/3-methoxy-1-butanol mixture, a solution of yttrium 2-methoxy-1-propoxide in 2-methoxy-1-propanol (8.81 grams), containing 2.5 weight % yttrium, was added. The solution was stored at room temperature for a period of two weeks, and no visible decomposition or precipitate formation was observed. ~ost o~ the solvent was evaporated from the sample, and the remaining material was dissolved in a trimethylbenzene/3-methoxy-1-butanol 1:1 mixture to form a solution containing 5 weight % of copper, barium and yttrium metals combined. The thin oxide film that was formed by a spin-on coating technigue using this solution was of good quality.

Ten grams of copper di-methoxide was suspended in lOO
mL of toluene. The reaction mixture was then quickly warmed to reflux, and lOO mL of 3-methoxy-l-butanol were added.
The temperature was th~n quickly raised to 125C, and the suspension was spargsd with nitrogen. After a short period of time, a very viscous solution was formed, and the sparging with nitrogen was continued for ten more minutes.
The viscosity of such prepared di-3-methoxy-l-butoxy copper solution was very substantially lowered by addition of lo mL
of di-2-methoxy-l-propoxy barium.
At this point, a much more efficient removal of methanol formed during exchange reaction (l) was possible.

Cu(OMe)2 ~ 2 HOCH2CH2CH(OMe)CH3 ------->
CUtOCH2CH2CH(OMe)CH3]2 + 2 MeOH tl) After five more minutes of sparging with nitrogen a mixture of di-2-methoxy-l-propoxy barium and tri-2-methoxy-l-propoxy yttrium in 2-methoxy-l-propanol (containing 0.052 mole o~ Ba and 0.026 mole of yttrium) was added. Complete solubilization of copper was achieved. The final concentration of metals was; 1.3 weight % Cu, 2.0 weight % Ba and 0.6 weight % Y.

2~6~)~

Erbium metal (25 grams o~ 40 mesh powder) was suspended in a mixture of 50 mL of toluene and 150 mL of 3-methoxy-l-butanol. After ten minutes of stirring at room temperature, 30 mg of HgC12 were added, and the reaction mixture was stirred for a period of four hours at 85C. No reaction was observed. The reaction mixture temperature was then raised to 128C. An exothermic reaction started after an additional hour of stirring. At this point, the stirring was continued ~or four more hours to achieve complete metal solubilization. After cooling, the reaction mixture was filtered to yield 253 grams of solution containing 8.5 weight % of erbium.

Europium metal (5 grams) was suspended in tolusne, and 40 mg of HgC12 was added. The metal suspension was placed in a ultrasonic cleaning bath ~or a period of twelve minutes. To such activated metal suspension, were added 30 mL of 3-methoxy-1-butanol. The reaction mixture was warmed to 128C and was stirred ~or a period of two hours. The reaction with alcohol started quickly without a long induction period. The product was ~iltered, and the filter cake was washed with trimethylben~ene. The resulting orange solution ~39.3 grams) contained 7.3 weight % europium.

2~26~

Neodymium metal ~25 grams in a form of small chunks) was wet ground in trimethylbenzene with 50 mg of HgC12 for a period of ten minutes. To the suspension of such activated neodymium metal was added 100 mL of 3-methoxy-1-butanol, and the reaction mixture was warmed to 128C. At this point, a fast and exothermic reaction was observed. The reaction temperature was maintained a~ 129C ~ 1 for a period of five hours. After filtration, 242.0 grams of blue solution containing 9.0 weiight % neodymium was isolated.

Terbium metal (100 grams) was suspended in dry xylene and 0.140 gram of HgC12 was added. The metal suspension was placed in an ultrasonic cleaning bath for a period of twelve minutes. To the suspension of such activated terbium metal was then added 20 mL of 3-methoxy-1-butanol, and the reaction mixture was warmed to 125C. At *his point, a fast and exothermic reaction was observed. ~he reaction temperature was maintained at 128C + 1 for a period of four hours. During this time, 300 grams of 3-methoxy-1-butanol were added in 20 mL portions. After filtration and washing of solid by-products with xylene, 700 yrams of a yellow solution of terbium 3-methoxy-1-butoxide was isolated.
i This reaction was conducted as in Example 10 using 100 grams of gadolinium metal in place of terbium. The product had to be filtered hot because of its high viscosity.

2~

Yttrium metal (15 grams) was suspended in toluene (200 ml). The mixture was heated to reflux, and 2-methoxyethanol (~0 grams~ was added dropwise. Reflux was maintained for three hours after the addition was completed, whereupon more 2-methoxyethanol (80 grams) was charged to the mixture. After another three hours at reflux, the mixture was cooled and was filtered through CELITE filter aid. The filtrate was stripped to dryness yialding a very viscous light brown oil. The alkoxide, Y(OCH2CH2OCH3)3, was soluble in toluene as well as in the parent alcohol (2-methoxyethanol).

Barium metal shot (22.3 grams) was placed into a flask with toluene (150 ml). The toluene was brought to reflux followed by the slow addition of 2-methoxyethanol (50 ml). After the evolution of hydrogen ceased, the reaction mixture was allowed to cool to room temperature and was filtered. Filtration yielded a brown colored filtrate.
The volatiles were removed~from the filtrate to yield a brown oil. The resultant oil, containing Ba(OCH2CH20CH3)2, remained in this state for more than 2 weeks without any solid precipitating out.

This Example has two parts. Part A describes an attempted synthesis outside the scope of the invention.
Part 8 describes the formation of lanthanum alkoxyalkoxides within the scope of this invention.

AST 54 9 -12~
Z~ 6 Part A (Comparative Run) Ten grams of lanthanum metal were suspended in 250 cc of ethanol. The reaction mixture wa~ refluxed for eight hours. At the end of the reflux there was no evidence of reaction.
Part B
The ethanol was distilled off from the reaction mixture of Part A. 250 cc of methoxyethanol were added and the reaction mixture was heated to reflux. The reflux evidenced evolution of hydrogen and was continued for twenty-four hours. The brown product was filtered and the filtrate stripped. A viscous oil t18 grams of La(OCH2CH20CH3)3~ remained. This product was dissolved in toluene to give a 21% by weight solution.

Twenty-five grams of calcium metal were milled in a ball mill for eight hours with 875 grams of stainless steel balls and 0.1 gram of HgC12. 7.3 grams of milled calcium metal were recovered.
- The calcium metal (0.18 mole) was added to 250 cc of methoxyethanol over a thirty-minute period and was heated to reflux temperature. The mixture evidenc~d vigorous hydrogen evolution. The reflux was continued for six, hours and the reaction product ~as then filtered to remove unreacted metal. The xesulting filtrate had a dark color which becamP
darker upon standing. The ~iltrate was then stripped and 32.6 grams (34.2% theoretical yield) of a dark viscous oil, comprising calcium methoxyethoxide, remained.

AST 5439 ~13-~2~ 6 The foregoing Examples are intended to illustrate certain embodiments of the present invention but should not be construed in a limiting sense. The scope of protection that is sought is set forth in the claims which follow.

Claims (24)

1. Metal compounds of the formula M(OR'OR'')x, where x is the valence of the metal M, R' is alkylene, R" is alkyl and M is a superconductor precursor metal other than copper and barium, which are essentially free of alkali and halide contamination.

2. Compounds as claimed in Claim 1 wherein M is selected from the group consisting of groups IIA, IIIB and VA of the Periodic Table.

3. Compounds as Claimed in Claim 2 wherein M is selected from the group consisting of calcium and strontium.

4. Compounds as claimed in Claim 2 wherein M is selected from the group consisting of scandium, yttrium, lanthanum and the rare earth metals.

5. Compounds as claimed in Claim 2 wherein N is bismuth.

6. Compounds as claimed in Claim 1 wherein R' and R" total from about 3 to about 8 carbon atoms and R" is from C1 to C4.

7. Compositions for use in the formation of metal oxide superconductors which comprise: (a) an organic solvent; and (b) dissolved in the organic solvent a metal compound of the formula M(OR'OR")x, where x is the valence of the metal M, R' is alkylene, R" is alkyl, and M is a superconductor precursor metal other than copper and barium, the metal compound being essentially free of alkali and halide contamination.

8. Compositions as claimed in Claim 7 wherein M is selected from the group consisting of groups IIA, IIIB and VA of the Periodic Table.

9. Compositions as Claimed in Claim 8 wherein M is selected from the group consisting of calcium and strontium.

10. Compositions as claimed in Claim 8 wherein M is selected from the group consisting of scandium, yttrium, lanthanum and the rare earth metals.

11. Compositions as claimed in Claim 8 wherein M is bismuth.

12. Compositions as claimed in Claim 7 wherein R' and R" total from about 3 to about 8 carbon atoms and R" is from C1 to C4.

13. A process for forming a metal compound of the formula M(OR'OR")x, where x is the valence of the metal, R' is alkylene, R" is alkyl, and M is a superconductor precursor metal other than copper and barium, which are essentially free of alkali and halide contamination which comprises reacting the metal M, with one or more alkoxy alcohols of the formula R"OR'OH to yield the metal compound solubilized in the alkoxy alcohol.

14. A process as claimed in Claim 13 wherein M is selected from the group consisting of groups IIA, IIIB and VA of the Periodic Table.

15. A process as Claimed in Claim 14 wherein M is selected from the group consisting of calcium and strontium.

16. A process as claimed in Claim 14 wherein M is selected from the group consisting of scandium, yttrium, lanthanum and the rare earth metals.

17. A process as claimed in Claim 14 wherein M is bismuth.

18. A process as claimed in Claim 13 wherein R' and R" total from about 3 to about 8 carbon atoms and R" is from C1 to C4.

19. A process for forming a metal compound of the formula M(OR'OR")x, where x is the valence of the metal, R' is alkylene, R" is alkyl, and M is a superconductor precursor metal other than copper and barium, which are essentially free of alkali and halide contamination which comprises reacting the alkoxide of the metal, M, with one or more alkoxy alcohols of the formula R"OR'OH to yield the metal compound solubilized in the alkoxy alcohol.

20. A process as claimed in Claim 19 wherein M is selected from the group consisting of groups IIA, IIIB and VA of the Periodic Table.

21. A process as Claimed in Claim 20 wherein M is selected from the group consisting of calcium and strontium.

22. A process as claimed in Claim 20 wherein M is selected from the group consisting of scandium, yttrium, lanthanum and the rare earth metals.

23. A process as claimed in Claim 20 wherein M is bismuth.

24. A process as claimed in Claim 19 wherein R' and R" total from about 3 to about 8 carbon atoms and R" is from C1 to C4.