Method of preparing inorganic-alkali metal salts

The present invention is directed to a method of preparing an inorganic-alkali metal salt of the formula: EQU ZY wherein Z is an alkali metal selected from the group consisting of lithium and sodium, and wherein Y is an inorganic radical selected from the group consisting of SCN, CN, CNS, OCN, Br, I, Cl, NO.sub.2, NO.sub.3, ClO.sub.4, ReO.sub.4, and CF.sub.3 SO.sub.3. The method involves the reaction of a nitrogen-containing compound of the formula: EQU QHY wherein Q is selected from the group consisting of specified nitrogen-containing groups, and wherein H is hydrogen and Y is as defined above, with an alkali metal compound of the formula: EQU ZX wherein Z is defined above and wherein X is selected from the group consisting of hydrogen, specified nitrogen-containing radicals, and specified organic radicals. The reaction is carried out in ether solvent. In a preferred embodiment, Q is NH.sub.3 and X is hydrogen.

BACKGROUND OF THE INVENTION AND PRIOR ART 
1. Field of the Invention 
The present invention relates to a method of preparing high purity, 
anhydrous alkali metal salts of the inorganic-alkali metal type. More 
particularly, the present invention is directed to the method of preparing 
such compounds by reacting specified nitrogen-containing compounds with 
specified alkali metal-containing compounds, as more fully developed 
below. 
2. Description of the Prior Art 
There have been many techniques developed over the past few years for the 
synthesis of inorganic--as well as organic--alkali metal salts. For 
example, Kunze et al, J. Phys. Chem. 67, 385 (1963) describe the 
preparation of lithium tetraphenyl boride by the reaction of sodium 
tetraphenyl boride with lithium chloride in ethanol, and Bhattacharyya et 
al, J. Phys. Chem. 69, 608 (1965) describe the preparation of alkali metal 
tetraphenyl boride salts by the reaction of sodium tetraphenyl boride with 
lithium chloride in THF solvent. Revzin et al, Chemical Abstracts 70, 
28974 q (1969) and Chemical Abstracts 71, 3416 s (1969) describe the 
preparation of lithium tetraphenyl boride from various salts, including 
ammonium tetraphenyl boride with lithium-containing ion exchange resins in 
acetone. Likewise, Kirgintsev et al, Chemical Abstracts 72, 139078 m 
(1970) describe the formation of lithium tetraphenyl borate and sodium 
tetraphenyl borate using potassium tetraphenyl borate with an ion exchange 
resin of the lithium form and using acetone solvent. Kozitskii, Chemical 
Abstracts 79, 83825 c (1973) describe the preparation of lithium 
tetraphenyl borate and the like by reaction of the potassium analogue with 
a lithium-containing ion exchange resin in the presence of acetone and 
water. (It should be noted that various prior art references refer to the 
same compounds as tetraphenyl borate or as tetraphenyl borides). Khol'kin 
et al, Chemical Abstracts 85, 86471 u (1976) describe the preparation of 
lithium tetraphenyl boride from sodium tetraphenyl boride but do not 
describe the source of lithium except to point out that it is an exchange 
synthesis, i.e., exchange extraction synthesis. Witting et al, Ann. 563, 
110 (1949) and Chemical Abstracts 46, 6607 d (1952) respectively teach the 
preparation of lithium tetraphenyl boride and the like from triphenyl 
boron and trifluoro boron sources reacted with lithium phenyl salt in 
ether solvents. Grassberger et al, Angew. Chem. Int. Ed. Engl. 8, 275 
(1969) describe the preparation of various alkali metal tetraorganyl 
borates by reaction of, for example, triphenyl boron with lithium 
tetraethyl boride without solvent. 
Lee, Inorg. Chem., Volume 3, No. 2, February 1964, pp. 289-90 describes the 
synthesis of lithium thiocyanate from hydrated lithium hydroxide and 
ammonium thiocyanate. Olah et al, Journal of the American Chemical 
Society, 97, No. 12, pp. 3559-3561 (1975) describe the synthesis of 
LiO.sub.2 CCF.sub.3 from lithium hydride and NH.sub.4 0.sub.2 CCF.sub.3. 
Morosi et al, Chemical Physics Letters, Volume 47, No. 2, pp. 396-398 
(1977) describe a theoretical analysis of a hypothetical reaction between 
the ammonium ion and lithium hydride in the gas phase to yield lithium 
salts. U.S. Pat. No. 3,049,406 describes the preparation of anhydrous 
lithium salts, including lithium halides, lithium pseudohalides, such as 
lithium cyanide and lithium thiocyanate, by the reaction of lithium 
hydride with halogens, cyanogen or thiocyanogen in an ether solution. 
Notwithstanding all of the aforementioned prior art directed to various 
methods of preparing alkali metal salts, to date no reference has been 
published which teaches or renders obvious the methods of preparation 
described herein. 
BRIEF DESCRIPTION OF THE INVENTION 
The present invention is directed to a method of preparing an inorganic 
alkali metal salt of the formula: 
EQU ZY (1) 
wherein Z is an alkali metal selected from the group consisting of lithium 
and sodium, and wherein Y is an inorganic radical selected from the group 
consisting of SCN, CN, CNS, OCN, Br, I, Cl, NO.sub.2, NO.sub.3, ClO.sub.4, 
ReO.sub.4, and CF.sub.3 SO.sub.3. 
The method involves the reaction of a nitrogen-containing compound of the 
formula: 
EQU QHY (2) 
wherein Q is selected from the group consisting of specified 
nitrogen-containing groups, wherein H is hydrogen and wherein Y is as 
defined above, with an alkali metal compound of the formula: 
EQU ZX (3) 
wherein Z is defined above and wherein X is selected from the group 
consisting of hydrogen, specified nitrogen-containing radicals, and 
specified organic radicals. The reaction is carried out in ether solvent. 
DETAILED DESCRIPTION OF THE INVENTION 
The present invention is directed to a method of preparing an 
organic-alkali metal salt of the Formula (1) described above, namely: 
EQU ZY 
wherein Z is an alkali metal selected from the group consisting of lithium 
and sodium, and wherein Y is an inorganic radical selected from the group 
consisting of SCN, CN, CNS, OCN, Br, I, Cl, NO.sub.2, NO.sub.3, ClO.sub.4, 
ReO.sub.4, and CF.sub.3 SO.sub.3. Of these, Y is desirably Br, I, CF.sub.3 
SO.sub.3 and SCN, with SCN being preferred. 
Included among the alkali metal salts which may be prepared by the present 
invention are: 
LiSCN 
NaSCN 
NaCN 
NaCNS 
NaOCN 
LiBr 
LiI 
LiCl 
NaNO.sub.2 
LiNO.sub.3 
LiClO.sub.4 
LiReO.sub.4 and 
LiCF.sub.3 SO.sub.3 
The method of the present invention involves reacting nitrogen-containing 
compound of the formula: 
EQU QHY (2) 
wherein Q is selected from the group consisting of NH.sub.3 ; 
N(CH.sub.3).sub.3 ; HN(CH.sub.3).sub.2 ; H.sub.2 NCH.sub.3 ; N(C.sub.2 
H.sub.5).sub.3 ; HN(C.sub.2 H.sub.5).sub.2 and H.sub.2 NC.sub.2 H.sub.5, 
wherein H is hydrogen and wherein Y is as defined above, in ether solvent 
with an alkali metal compound of the formula: 
EQU ZX (3) 
wherein Z is as defined above and wherein X is selected from the group 
consisting of H; NH.sub.2 ; N(CH.sub.3).sub.2 ; HNCH.sub.3 ; N(C.sub.2 
H.sub.5).sub.2 ; HNC.sub.2 H.sub.5 ; N(i-CH(CH.sub.3).sub.2);.sub.2 
--CH.sub.3 ; --C.sub.2 H.sub.5 ; and --C.sub.6 H.sub.5. 
Desirably, the variable Q in Formula (2) is selected from the group 
consisting of NH.sub.3 and the mentioned tertiary amines, and is 
preferably NH.sub.3. Desirably, the variable Y in Formula (2) is selected 
from the group consisting of Br, I, CF.sub.3 SO.sub.3 and SCN, and is 
preferably SCN. 
In the alkali metal compound of Formula (3) above, the variable Z is 
lithium or sodium and is preferably lithium. Also, the variable X is 
desirably hydrogen, NH.sub.2 ; N(CH.sub.3).sub.2 and HNCH.sub.3. 
The reaction of the present invention is performed in ether solvent, as 
mentioned. Among the ethers which may be employed are dioxolane, 
dimethoxyethane, diglyme, tetrahydrofuran, methyltetrahydrofuran, 
tetrahydropyran, dioxane and diethyl ether, as well as mixtures thereof. 
Desirably, the ether solvent may be diethyl ether, dioxolane, 
dimethoxyethane, 2-methyltetrahydrofuran and mixtures thereof. Preferably, 
the ether solvent may be selected from diethyl ether, dioxolane and 
2-methyltetrahydrofuran. 
In performing the synthesis of the present invention, the 
nitrogen-containing compound of Formula (2) is reacted with the alkali 
metal compound of Formula (3) in ratios so as to achieve a desirable 
amount of reaction product. Although it is not essential to the process, 
it is particularly advantageous to combine these two reactants so as to 
have a stoichiometric excess of the alkali metal compound of Formula (3). 
Concerning the ether solvent, it is desirable but not essential that 
adequate solvent be used so as to dissolve all of the desired reactant 
materials. In general, at least about 0.5 to about 50 milliliters of 
solvent per 1.0 gram of total reactants is useful. Preferably, at least 
about 2.0 to about 20 milliliters of solvent per 1.0 gram of total 
reactants may be used. 
These reactions may be carried out at any operable pressure and 
temperature, and room temperature and pressure conditions will allow these 
reactions to readily occur in most instances. It may also be advantageous 
to pass an inert gas such as N.sub.2, He, or Ar through or over the 
condensed reaction mixture so as to purge by-products including H.sub.2 
and volatile amines. Also, in some instances, it is preferable to employ 
elevated temperatures, especially at reflux temperatures of the 
solvent-reactant systems. For example, reaction temperatures in the range 
of about 0.degree. C. to about 175.degree. C. may be used. 
By the process of the present invention, significant advantages are 
achieved over prior art synthesis techniques. For example, by using the 
method of the present invention, anhydrous lithium salts may be obtained 
without requiring additional finishing steps to remove water. Also, the 
inorganic-alkali metal salts produced may be used in situ in their solvent 
solution, or they may be isolated in solid form by conventional separation 
techniques. Further, using the ZX type reactant, the need to carefully 
control the stoichiometric ratio of the reactants is eliminated. Due to 
the very limited solubility of some of these ZX type reactants, excess may 
be used and only that which is stoichiometrically required by the reaction 
dissolves and is consummed. The presence of excess ZX serves as a 
gettering agent capable of removing from the solvent traces of water which 
are often considered undesirable for alkali metal salt solutions. This 
added benefit insures an anhydrous solution which may be useful directly 
in high purity applications, e.g., as electrolytes in alkali metal anode 
batteries. 
The present invention is illustrated in detail by the following examples. 
However, these examples are presented for illustrative purposes only and 
the invention should not be construed to be limited thereto.

EXAMPLE 1 
Lithium hydride (4.70 g, 0.587 mole) and dioxolane (150 mL) are charged to 
a 250 mL flask, fitted with a magnetic stirrer, condenser, nitrogen inlet, 
and solids addition arm. through the latter anhydrous NH.sub.4 SCN (19.0g, 
0.25 mole) is added. A vigorous reaction results and ammonia is detected 
in the effluent gas stream. After stirring at reflux about 24 hours, the 
mixture is cooled and filtered. Unreacted LiH (2.6 g, 0.327 mole) is 
recovered indicating that 0.26 mole reacts with the NH.sub.4 SCN. 
Concentration of the clear filtrate yields 32 g of white solid which 
contains dioxolane as shown by NMR analysis in dimethoxyethane. 
Analysis 
Calc. for LiSCN Dioxolane, MW 139.060: C 34.52; H 4.35; N 10.07; Li 4.99. 
Found: C 31.91, 31.33, 31.10; H 4.30, 4.48, 4.52; N 10.50, 9.59, 9.77; Li 
5.10. 
Agreement between experiment and theory is very good for H, N, and Li in 
support of the solvate composition. Experience shows that low values for C 
are expected due to prevolatalization of complexed dioxolane and 
concommitant incomplete combustion. 
EXAMPLE 2 
NH.sub.4 SCN (39 g, 0.5 mole) and 500 mL of diethyl ether (dried over 
CaH.sub.2) were combined in a 1000 mL flask fitted with a reflux 
condenser, a magnetic stirrer bar, a nitrogen line, and a side arm 
attached by a short length of Gooch tubing to a 125 mL Erlenmeyer flask 
containing LiH (8.0 g, 1 mole). The LiH was added in portions over one 
hour and the reaction produced was sufficiently exothermic so as to bring 
the mixture to reflux. After heating the mixture at reflux for an 
additional 24 hours, the mixture was cooled and excess LiH was removed by 
filtration. Stripping the filtrate afforded about 45 g of crude, ether 
containing, product. This was evacuated at 10.sup.-3 Torr for one day at 
room temperature then two days at 95.degree.-98.degree. C. The final yield 
was 32.2 g (quantitative) of LiSCN which was free of ether as determined 
by an nmr analysis of a DME solution.