DE1212085B - Process for the electrolytic production of alkyl compounds of metals of main groups II to V and subgroups II - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

C07f

BOIk
German KL: 12 ο -26/03

Number: 1212 085

File number: Z8742IVb / 12o

Filing date: May 12, 1961

Opening day: March 10, 1966

The electrolytic production of metal alkyls of main groups II to V of the periodic table by electrolysis on a structural anode made of a metal, the alkyl compound of which is produced and a mercury cathode using complex organoaluminum electrolyte melts is the subject of numerous older patents of the inventor. Draw all of these known procedures is characterized by the fact that organoaluminum complex compounds as the electrolyte, namely in their Melt, are used, j

Further work in the field of electrolytic metal alkyl production described have now shown that considerable advantages are often achieved over the known processes can, if new types of electrolytes are used, with the rest corresponding to those worked out so far Knowledge can be proceeded.

The invention accordingly relates to a method for the electrolytic production of alkyl compounds of metals of the II. to V main group and the II. subgroup by electrolysis on a consumption anode from the metal whose alkyl compound is to be produced and a mercury cathode, which is characterized in that the electrolyte used is an alkali boron complex compound of the general formula

MeBR _m (OR ') »

and optionally also an alkali aluminum complex compound the general formula

used, where in these formulas Me is alkali metal, R is alkyl radicals with at least 2 carbon atoms, R 'and R "is an alkyl or cycloalkyl radical, m is a preferably integer from 1 to 4, η is a preferably integer from 0 to 3, ρ a preferably integer from 3 to 4 and q denotes a preferably integer from 0 to 1 and the sums m + n and p -] - q = 4. It can be particularly advantageous according to the invention to include the known The scope of the invention therefore includes both electrolytes exclusively containing boron-containing complex compounds and mixed electrolytes made from boron complex compounds and aluminum complex compounds.

The process according to the invention is very good for the preparation of metal alkyls with lower alkyl radicals suitable. In particular, it is suitable for the process for the electrolytic production of

Alkyl compounds of metals of

II. To V. main group and the II. Subgroup

Applicant:

Dr. Karl Ziegler,

Mülheim / Ruhr, Kaiser-Wilhelm-Platz 1

Named as inventor:

Dr. Karl Ziegler,

Dipl.-Chem. Dr. Herbert Lehmkuhl,

Mülheim / Ruhr

position of the metal ethyl compounds. A technically particularly important representative of these metal ethyl compounds is tetraethyl lead.

Of the complex boron compounds of the general formula

MeBR _m (OR ') »

the complex compound in which m = 4 and η = 0, i.e. the alkali boron tetraalkyl compound MeBR ₄ , has the highest conductivity. Accordingly, it is a preferred method of operation according to the invention to work with electrolytes which contain _{the complex compound MeBR 4.} In particular, with the sodium and / or potassium complex compound

MeB (- C ₂ H ₅ ),
worked.

The inventive method is now by no means limited to working only with the last-mentioned tetraalkyl complex compounds. It is precisely an essential advantage of the invention that different types of mixed electrolytes are used can be so that an adaptation of the chemistry in the electrolyte to the respective reaction conditions and reaction results succeed in a way that has not been possible before.

In one of these embodiments according to the invention, mixed electrolytes are made from the boron compounds the general formula

and organoaluminum complex compounds of the general formula

609 537/443

are used, in which Me is sodium and / or potassium and aluminum compound AlR ₂ OR "can also mean considerable R an ethyl radical. Bring advantages. Thus, it is a particularly inert compound in the mixed electrolyte of boron and aluminum electrolyte system, which are minium complex compounds In particular, two that do not tend to decompose at the cathode are called characteristic types. In one embodiment, a mixture of the boron complex simplifications will be possible in the one embodiment, which may result in a considerable procedural form. Reference will be made to a special case of the connection MeBR ₄ with the complex aluminum _{Furthermore, MeAlR 4} can be used through the connection. In the electrolysis, a suitable choice of the radical R "the boiling temperature of this mixed _{electrolyte is created as long as boron and this free aluminum compound AlR 2} OR" is present in the electrolyte, freely selected as anodic io relatively wide limits decomposition p roduct of the electrolyte is always free. This makes it possible to adapt to the respective BR ₃ . This is created on the one hand by direct decomposition ratios additional relief for a setting of the complex compound MeBR ₄ , on the other hand possible separation of the reaction by distillation reacts to create _{any anodic free AlR 3 products.}

immediately with the complex boron compound according to the 15 Another mixed electrolyte of the invention used

Equation: Mixtures of different boron compounds of the general

AlR ₃ + MeBR ₄ -> MeAlR ₄ + BR ₃ ^{my formula}

This embodiment of the invention

Procedure can have significant advantages. In particular, mixtures of acidic-general ones, the conductivity of the complex, substance-free and oxygen-containing boron complex compound-alkali aluminum compounds is higher than that of the fertilizers. The combination complexes alkali boron compounds shown here. On the other hand, which are only examples of the procedure, as an anodic decomposition product of the invention, show that it is highly volatile _{with the new free standing BR 3} In contrast to the free AlR ₃ electrolyte or electrolyte mixture, the electrolyte bath is particularly difficult to counteract a subsequent disturbance, namely in a way that separation of this decomposition product is not necessary, or has not been possible so far. The free BR ₃ tends Furthermore, in contrast, when working with pure boron-containing electrolytes, to AlR ₃ neither to undesired decomposition, especially when working with sodium or with cathodically deposited sodium potassium boron tetraethyl, it can be useful to use one or cathodically occurring potassium amalgam Measure according to the invent not to be taken when working with pure organoaluminum. The Alkalibortetraäthyle have enamel electrolytes for these two cases, ie for the points, which are relatively high. (Mp. Cathodic sodium deposition or for the cathodic 35 NaB (C ₂ H ₅ ) ₄ = 145 ° C; KB (C ₂ H ₅ ) ₄ = 159 ° C). The Verdian formation of potassium amalgam, special use of these compounds in which melt flow control measures must be taken, electrolysis can cause difficulties as a result, with the boron-containing electrolytes according to the invention, however, if these compounds according to the invention are disregarded, these precautionary measures are disregarded in a suitable polar solvent, so unless other electrolysis products such 40 they require precautionary measures at temperatures between room temperature. Lightly electrolyze in the last temperature and 150 ° C. Surprisingly described embodiment of the mixed electrolyte, it was found that such solutions of the organic complex compounds previously only used in melts, thus the high conductivity of the aluminum electrolyte compounds used in melts, are excellently suitable as electrolyte baths. In the mentioned chemical indifference of the free BR ₃ 45 of this embodiment of the invention will therefore be connected. In this embodiment, electrolysis containing polar inert solvents is expediently used at the time trolyte. This embodiment is also terminated at which the formation of free AlR _{3 is} not restricted to specific compounds, it begins. In particular, it is preferred here to use the proportions of more complex 50 decomposed for the electrolysis method according to the invention.

Boron compound intermittently or preferably continuously It is preferred in this form of the process

need to be added. to use organic polar solvents. Examples

In another embodiment of the invention for this purpose, the complex tetraalkylboron compound is aromatic hydrocarbons, but especially tertiary amines with the aluminum complex compound MeAlR ₃ OR "55 and preferably ethers. Particularly open-chain or used The oxygen-containing aluminum complex agent mentioned as an excellent solution for carrying out the binding according to the invention according to the following reaction equation: Method shown: Examples of open-chain ethers

BR ₃ + MeAlR ₃ OR "-> MeBR ₄ + AlR ₂ OR" _β ^s j? ^d . DMkyl ethers, such as diethyl or dibutyl ethers.

* ' ^a 60 Polyethers are also suitable, e.g. B. Dialkyl ethers of

In the presence of these oxygen-containing aluminum glycols. However, cyclic ethers are preferred,

complex compounds thus arise as separable and indeed cyclic ethers of the type of tetrahydro-

Decomposition product of the electrolyte not free furans. Another example of such a cyclic

Boron trialkyl, but the oxygen-containing aluminum ether is dioxane. As tertiary amines z. B.

compound AlR ₂ OR ". Of course, triethylamine and dialkylaniline can also be considered.

the boron compound with the two types mentioned In a particular embodiment of the invention

of aluminum complex compounds together, sodium or potassium boron tetraalkyl complex

be turned. The formation of oxygen-containing compounds can be used in aqueous solutions.

5 6

It is known that the Tetraäthylborkomplexver- Is as a decomposition product of the electrolyte free bonds below 70 ° C largely hydrolysis boron trialkyl accrued, so it can z. B. are changing constant. The use of such aqueous settlement with alkali metal, hydrogen and olefin or electrolyte solutions is naturally limited because, by reaction with alkali metal and alkyl halide, it can only be used again in the complex alkali boron tetraalkyl compounds to produce hydrolysis-resistant metal compounds. Examples of this are the ethyl be converted. The same applies to the compounds of mercury, tin, lead, antimony and alkyl-substituted boric acid esters. If desired, and bismuth. Can free boron trialkyl during the electrolysis or If you work with electrolytes, which as anodic outside of the electrolysis device deliver a free boron compound in a decomposition product, io speaking aluminum compound, in particular in this way the use of relatively high-boiling solder aluminum compounds of the formula AlR ₂ OR Solvents are preferred. This then escapes. From this, for example, the free boron trialkyl from the electrolyte solution, a treatment with alkali metal, hydrogen and olefin solution of the metal alkyl formed in the solvent or by treatment with alkali metal and alkyl and residual electrolytes This can easily be separated from the corresponding alkali metal aluminum by distillation. Complex compound can be obtained The preparation of new amounts of free boron trialkyl under electrolyte-analogous conditions. The electrolysis formation of the alkali metal boron tetraalkyl complex compound temperature _{should not exceed the decomposition temperature of the metal formation and the compound AlR 2} OR "in the ethylene cycle Operate at the regeneration process.
Magnesium, but can also have higher Grenztem- For use in the process according to the invention temperatures, z. B. about 150 ° C, can be selected. If the following metals are particularly suitable: beryllium, aqueous solutions, then the limit magnesium, mercury, aluminum, indium, thallite temperature is determined by the hydrolysis resistance of the um, lead, tin, antimony, bismuth,
organic complex compound determined. In general, the upper limit temperature here is 60 to 70 ° C.

The conductivity of the Alkalibortetraäthyle is in example!
these possible temperature ranges between 10 ² 30
and 10 " ¹ O ^-1 cmr ¹ and thus in a range that

the previously known aluminum compounds by electrolyzing a solution of 27 g (0.18 mol) of is equivalent. Sodium boron tetraethyl in 50 g of water in a protective The separation of the reaction mixture is simple. gas atmosphere (nitrogen, noble gases) between a normal case, a simple distillation is sufficient to 35 cathode made of 100 ml of mercury and a disk the individual components, namely anodic shaped anode made of lead, which are at a distance from the decomposition product of the electrolyte (if 10 mm above the Mercury surface rotates (if present), solvent, formed metal ^{ethyl, an effective electrode surface of 0.3 dm 2} each and residual electrolyte. Should Difficulty and a current density of 10 A / dm ² is the potencies arise that z. B. anodic cell voltage about 2.7 V and does not rise sharply until towards the end of the settlement products and metal alkyl formed, similar to electrolysis. If the cell voltage has reached 6 V boiling point, you can interrupt it by controlling the. On the aqueous chemistry in the electrolyte, e.g. B. through the described layer a second liquid phase has accumulated, bene choice of mixed electrolytes, here a sufficient one, which is separated and distilled under protective gas. One de boiling difference can be created. Another 45 receives 15.4 g of boron triethyl, b.p. 94 ⁰ C, and 12.8 g of lead Advantage of the invention when working with electrolytes, tetra-ethyl, b.p. ₁₈ 90 ⁰ C (90%, based on the boron-containing and thus low-boiling decomposition reversed, coulometrically measured amount of electricity from products can be that the resulting 4.725Ah). The mercury contains all of the metal alkyl that does not need to be distilled. Sodium deposited during the electrolysis only needs to be ensured that the released 50 (4.05 g).
Boron compound and that optionally used

Solvent at sufficiently low temperatures R · ■ "19

be driven off from the metal alkyl formed. e ι s ρ 1 e
This then remains as a distillation residue.

According to the invention, it is preferred to use a 55 In an apparatus as described under 1

To work the mercury cathode, as it is in the patent, a solution of 31.5 g (0.19 mol) of potassium

1161 562 is described. boretetraethyl in 90 g of water between a cathode

In order to achieve the optimum in economic efficiency in the new one made of mercury and an anode made of antimony.

To obtain the method, it is - as in the case of a current density of 3.5 A / dm ² , the already known electrolytic method of the 60 cell voltage input is about 2.1 V. When the

Applicant for the production of metal alkylene voltage has risen to 6 V, one interrupts.

expedient, with regeneration of the consumed After separating the uppermost liquid phase and

14.8 g of boron triethyl are obtained from electrolytes and their decomposition products for distillation

fresh usable electrolyte to work. and 10.8 g of antimony _{triethyl, boiling point 10} 43 ⁰ C (82% of this is based on the amount of electricity used up to now 65 of 5.07 Ah). That

a variety of ways. In the following only one potassium (7.38 g) deposited by electrolysis

Selection of various useful options is in the mercury,

described. The following can be represented in an analogous manner:

7th Metal alkyl Kp. ₁₀ = Current density 8th Current efficiency 3. Tin tetraethyl
4. Mercury diet 48 ° C
38 ° C 3.5 A / dm ²
3.5 A / dm ² Cell voltage 10%
86% 3.4V
2.5V

Mercury electrodes placed next to one another are used to represent dietary mercury and lifts the mixture of the reaction products boron triethyl and mercury diethyl, which are heavier than Water is, from time to time, off the anode surface.

Example 3

The electrolysis cell is a glass tube with a capacity of 11 with a flat edge that goes through a cover made of aluminum or plastic, also ground flat, e.g. B. a phenol-formaldehyde condensation product, is tightly closed. There are 5000 g of mercury on the bottom of the nozzle. At a distance of about 5 mm above the A disk-shaped anode made of lead, which doubles as a stirrer, rotates on the surface of the mercury Electrolyte is used and is therefore still equipped with numerous side blades. The lead disk is screwed into a vertical axis. Another glass stirrer leads through the hollow shaft of the stirrer, which stirs the mercury at a rotational speed of 10 rpm, while the lead anode rotates quickly. The lid of the vessel has holes to accommodate a thermometer and the Power supply for the cathode, a screwed-in ground joint sleeve for attaching a reflux condenser, a nozzle for the passage of protective gas and the agitator bearing for the rotating lead anode.

A solution of 250 g of NaB (C ₂ Hj) ₄ in 400 cm ^{3 of} tetrahydrofuran was poured into this cell under protective gas and electrolyzed at 3.8 A, that is 14 A / dm ² , at 90 ° C. for 7 hours. _{A solution of 210 g of —Na (C 2} Hj) ₃ AlOC ₄ H ₉ in 150 cm ^{3 of} tetrahydrofuran is allowed to flow continuously from a storage vessel at the rate of passage of the current over the course of 7 hours. After 26.8 Ah has passed through, the electrolysis is terminated and the reaction mixture is separated by distillation. It distilled over a 50 cm Vigreux column ^3, first at atmospheric pressure, the tetrahydrofuran off, then with 1 to 3 Torr and 40 to 5O ⁰ C and then the lead tetraethyl at 110 to 120 ° C, the

Al (C ₂ Hj) ₂ OC ₄ H ₉

which is then reintroduced in a known manner with NaH and ethylene

NaAl (C ₂ Hg) ₃ OC ₄ H ₉

transferred, dissolved in part of the recovered tetrahydrofuran and fed to a new electrolysis. The distillation residue is NaB (C ₂ Hj) ₄ , it is dissolved in 400 cm ^{3 of} solvent and used again as an electrolyte. The yield of tetraethyl lead is 75 g (= 93% of theory). The sodium amalgam is 0.46%, consequently contains 23 g of sodium (= 100% of theory).

65 Example 4

With a suitable modification of the electrolysis cell, the same procedure as in Example 3 Mercury diet can also be represented. To do this, place a on the bottom of the electrolysis vessel about 3 cm high glass bowl with a diameter half the diameter of the electrolysis vessel owns. Both the bowl and the bottom of the electrolysis vessel are now about 2.5 cm high Filled with mercury, one portion in the bowl serves as the anode, the other as the cathode. Close above the surface of the mercury is allowed to rotate a stirrer rapidly. The reaction mixture is worked up analogously to Example 3. The yield of Mercury diet is 120 g (= 93% of theory).

Example 5

In the apparatus described in Example 3, a solution of 206 g of NaB (C ₃ H _{7) 4} ³ electrolyzed in tetrahydrofuran 300 cm at 90 ⁰ C for 7 hours with 3.8 A. A lead anode is used. A solution of 194 g of Na (C ₃ H ₇ ) ₃ BOCH ₃ in 250 cm ^{3 of} tetrahydrofuran is continuously added dropwise over the course of 7 hours at the rate of passage of the current. After the passage of 26.8 Ah, the electrolysis is stopped. The reaction mixture is now separated by fractionation - after the tetrahydrofuran has been distilled off - at 0.1 torr in 128 g of B (C ₃ H ₇ ) ₂ OCH ₃ and 90 g of lead tetrapropyl (= 95% of theory).

Example 6

The electrolysis in the apparatus described in Example 3 with a melt of 300 g of NaB (C ₂ Hj) ₄ at 150 ⁰ C with a current intensity of 3.8 A using a Mg anode. The terminal voltage is 3.5 V. The electrolysis cell is equipped with an effective reflux condenser. _{A melt of 332 g of Na A1 (C 2} H ₅ ) _{4 is} allowed to run in at the rate of current passage over the course of 7 hours. After 2 × 26.8 Ah has passed through, the reaction mixture is allowed to cool. A liquid phase containing boron triethyl and magnesium diethyl in a ratio of 2: 1 separates out above the solidifying complex salt phase. The liquid phase is siphoned and up to 150 ⁰ C all Bortriäthyl distilled off by heating to 140th

190 g of boron triethyl (that is 97% of theory) are obtained as distillate and 65 g of magnesium diethyl (= 73 o / _o ) as solid distillation residue. The boron triethyl can be converted back into NaB (C ₂ H ₅ ) ₄ in a known manner with NaH and ethylene. The solid complex salt phase in the electrolysis vessel is NaAl (C ₂ H ₅ ) ₄ . Both of the recovered complexes can be used for re-electrolysis.

Claims (5)

Patent claims: 1. Process for the electrolytic production of alkyl compounds of metals from II. To V. main group and the II. Subgroup by electrolysis on a consumption anode from the Metal, the alkyl compound of which is to be produced should, and a mercury cathode, thereby characterized in that the electrolyte used is an alkali boron complex compound of the general formula and optionally also an alkali aluminum complex compound the general formula MeAlR ₂₁ (OROi 10 used, where in these formulas Me is alkali metal, R is alkyl radicals with at least 2 carbon atoms, R 'and R "is an alkyl or cycloalkyl radical, m is a preferably integer from 1 to 4, η is a preferably integer from 0 to 3, ρ a preferably integer from 3 to 4 and q denotes a preferably integer from 0 to 1 and where 10 continue to be the sums of m + n and p + q = 4. 2. The method according to claim 1, characterized in that an electrolyte of the general formula MeBR _{4 is} used. 3. The method according to claim 1 and 2, characterized in that one additionally indifferent, polar organic solvents used. 4. The method according to claim 1 and 2, characterized in that alkali boron tetraalkyls in aqueous solution used. 5. The method according to claim 1 to 4, characterized in that the decomposition products of the electrolyte is regenerated and reused for electrolysis in the circuit. Legacy Patents Considered:
German Patent No. 1175 233. 609 537/443 3.66 O Bundesdruckerei Berlin