DE1803524A1 - Ruthenium compound and process for its preparation - Google Patents

Description

DR.-ING. G. Eichenberg ₄ Dusseldorf _{t the} October 16, 1968 DIPL-ING. H. SAUERLAND Cecilienallee 76 Ill / Sehn DR.-ING. R. KING PATENT LAWYERS Our file: 24 406

International Nickel Limited,! Names House, Millbank,

London, SW 1 , England

"Ruthenium compound and method for its

Manufacture "

The invention relates to a new ruthenium compound and to a method for the same Manufacture and electroplating of ruthenium including the associated ruthenium-containing Baths.

Electrically deposited ruthenium coatings are particularly suitable for electrical contacts, for example for switching measures, as well as for wear-resistant surfaces. The well-known galvanic baths for electrolytic deposition of ruthenium can only be produced commercially with difficulty in a reproducible manner and are subject to heavy sludge formation during electrolysis.

The invention is therefore directed to new ruthenium compounds which are in aqueous solution extremely suitable as an electrolyte for the galvanic deposition of ruthenium.

The ruthenium compounds according to the invention, in which the ruthenium is present as an anionic complex

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have the following gross formulas:

where Y and y represent a chlorine or bromine group and

χ = 2, 3 or 4

x + y a 10 and

ζ = 5 - χ
are.

The nature of the anionic ruthenium complex will be explained in more detail later. But the reasons are the following for the individual numerical values in the gross formula

The coordination number of ruthenium in the complex is 6. The nitrogen atom binds one valence of the two ruthenium torques, while the other ten valences are bound by Aquo-g chlorine or bromine groups. For this reason χ + y = 10 must be. The ruthenium atoms have four valences, so that the sum of the positive charges on ruthenium is eight. In contrast, nitrogen has a three-fold negative charge. If the remaining ten ligands are chlorine or bromine groups, for example anions with a negative overall charge ύοώ. ten, then the anionic complex has a five-fold negative charge. However, if some ligands are neutral aquo groups and the negative charge z- is reduced by one per aquo group, then ζ = 5 - x results.

Particularly preferred compounds according to

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Invention contain an anion complex with the following Gross formula:

Λ *

Z-

The compounds according to the invention are they are preferably salts of monovalent cations, in particular ammonium, lithium, sodium or Potassium salts

According to the invention, ammonium salts are used as the electrolyte for the galvanic deposition of ruthenium the general gross formula:

(NH ₄ )

preferred.

The ammonium salt of the bi-aquochlor complex ITlU ₂ N (H ₂ O) ₂ CiJI (NH ^) ₅ is prepared in such a way that an aqueous solution of ruthenium chloride ■ is heated with an excess of sulfamic acid until the sulfamic acid is hydrolyzed . The ammonium salt of the complex is thereby obtained in the reaction mixture. To recover the solids, the solution must normally fen by Eindamp- i followed by cooling, preferably to about ⁰ ° C, are brought to the saturation point, for example with ice water. The solid can then be separated off by filtration, but should be washed out with ice water in order to separate it from the water-soluble impurities, for example from sulfuric acid and ammonium sulfate and chloride.

The ruthenium chloride is often used commercially as a solution in hydrochloric acid. However, it should be a concern be careful to avoid excessive amounts of hydrochloric acid in the starting mixture, as this leads to formation

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of compounds that do not fall under the invention. It was found through tests be that in the commercial use of ruthenium chloride solutions in hydrochloric acid, the solution initially should be evaporated to a concentration of 100 g ruthenium in 300 ml acid solution.

After the reaction of ruthenium chloride with sulfamic acid in aqueous solution, it is advantageous to to add some hydrochloric acid to the solution in order to achieve an optimal yield of the aquochlorine complex according to the invention to reach. Such an addition of hydrochloric acid reduces the risk of bisulfate groups, for example enter the complex as ligands instead of the desired chlorine groups. The sulfate groups as ligands can occur in the absence of an adequate amount of chloride ions because of high concentrations of ammonium bisulfate and sulfuric acid can form in the reaction mixture. For this reason should per gram of ruthenium at least 3 ml more concentrated Hydrochloric acid can be added. The hydrochloric acid is added best after concentrating and cooling the reaction mixture, otherwise it would be annoying Form fumes.

A more or less large excess of sulfamic acid can lead to the formation of complexes with slightly different physical properties, which are possibly steric isomers. According to the method described, two samples A and B of TIlU ₂ N (H ₂ O) ₂ Ol ₈ I (NH.), According to Examples I and ΙΙΪ, were prepared with excesses of sulfamic acid of different sizes; they differed somewhat in terms of their physical properties

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Properties. When preparing the aquochlorine complex, 4 to 9 moles of sulfamic acid are preferably used per atom of ruthenium. Experiments have also shown that when the aqueous reaction mixture is prepared from solid hydrated ruthenium chloride instead of conventional ruthenium chloride solutions, a lower amount yield excess of Sulfamatsäure of for example 4 to 5 mol per atom Sulfamatsäure #-56 ruthenium better results. ä

The invention is explained below using a method for producing the complex

I ₃ explained in more detail.

Example I: An aqueous solution of ruthenium chloride with

■ z

50 g of ruthenium in 2000 cnr solution were circulated for 48 hours at the boiling point with 300 g of sulfamic acid. The solution was then evaporated to 500 cm and cooled to room temperature. The solution was then further ^{cooled to about 0} ° C. with ice water for about 3.5 hours and the complex was given a yield of 60 $ as a "dark red crystal (sample A), which was filtered off, washed with ice water and then dried Evaporation of the filtrate with subsequent cooling enabled a further 30 $ to be obtained, so that the overall yield was 909ε.

Example II;

An aqueous solution of ruthenium chloride with 50 g of ruthenium in 2000 cm × ⁵ was kept at the boiling point with 300 g of sulfamic acid and circulated for 48 hours. The solution was then evaporated ^{to 500 cm 5}

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»6 - ■

to room temperature aTbgekuh.lt · Then the solution followed by 3 _f 5 hours, 200 cm of concentrated hydrochloric acid _(cooled with ice water wnirde "from the solution was filtered off the complex in Porm donkelroter crystals with a yield of about 8SL ^, washed with EiBwasser and then dried. 300 em of distilled water were added to the piltrate and the solution was evaporated.

An aqueous solution of ruthenium chloride with 2.5 g of ruthenium in 1000 cm of solution was circulated in 15 states at boiling temperature with 100 g of sulfamate, then poured in and ^{cooled to about 0} ° C for 3 to 4 hours and then filtered. The complex was obtained in the form of reddish-brown iristallines, which were washed out with 80% aqueous acetone. This sample B had a far better solubility in water than sample A.

From the Aquoohlor complex OCIgI] ClBL)., Can be other compounds

manufacture »In the following example the representation of the corresponding Aquobrosakompl @ xes

(MH ^), Toeschritten »

example

A solution of 15 g

in 100 ml of water was 3 hours with 50 ml, analytical pure hydrobromic acid with a specific gravity of 1.47 overturned «The reaction göiaiseli was

9 0 9 8 21/10 6 8

then evaporated to 50 ml, cooled to room temperature and finally a brown crystalline reaction product [Ru ₂ N (H ₂ O) ₂ Br ₈ I (NH.), filtered off and washed out with ice water. The yield was about

While the previous examples related to the production of τοη ammonium salts of the complex, Other salts can also be prepared without further ado, but the ammonium salts are used as the starting substance to serve. This can be done, for example, in the usual way by ion exchange. After this Processes can include, for example, the corresponding hydrogen, sodium, potassium or other alkali metal salts getting produced. However, if the salt is to have a particularly high purity, it is advantageous Process used in which an ion exchange also takes place. One such procedure is described in the following exemplary embodiment.

Example V:

A solution of 5 g of [JEIu ₂ N (H ₂ O) ₂ Cl ₈ ] (NH ^) ₃ in 150 ml of water was passed through an ion exchange column at a rate of 2 to 5 drops per second. The column had a capacity of 270 ml and contained a synthetic resin cation exchanger in the form of a crosslinked polystyrene with SO ₂ OH groups (Zeo-Karb 225) o The solution residue was washed out of the column with distilled water. After the solution had evaporated completely, the hydrogen salt of the complex was obtained as a dark reddish-brown deliquescent solid.

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Although the ammonium salts are particularly suitable for galvanic baths, especially because they are easy to prepare, the other salts have other advantages, for example greater solubility, due to which a higher ruthenium concentration in the bath can be achieved, In addition, the ammonium and the other salts of a certain complex can be used as starting substances be wetted with different ligands to produce other complexes. This is explained in more detail in example IY described. Such a substitution of ligands is well known in coordination chemistry .

Although the complex compounds were described as compounds with an anionic complex of the general formula [^ Ru ₂ N (H ₂ O) υΊ ^z "", one must assume that they are complex ruthenium compounds with a nitrogen bridge, the anions of which are accordingly as follows Structural formula has:

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! Formula 4 t L

in which L corresponds to an aquo, chlorine or bromine ligand.

There are a number of clues as to that speak for such a structural formula.

Analytical investigations of the bi-aquo-chlorine complex QlU ₂ N (H ₂ O) ₂ Cl ₈ ] (NH ^) ₅ are in good quality

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- ίο «

Agreement with reeimerisehen results due to the connection in the form of the complex with an N-bridge, as can be seen from the table below results.

more analytical Weri 9.0 arithmetic • (50 9.2 47.0 48.1 NH, (ammonium 2.1 2Λ Cl 34.0 34.4 N (except ammonium) ■ 7.9 5.9 Ru H ₂ O (remainder).

The infrared spectrum of the aquo-chlorine complex ₂ O) ₂ OIqI (NH.), And the corresponding bromine complex (Ru ₂ N (H ₂ O) ₂ Br ₈ ] (NH ^), is indicated by a strong absorption in the vicinity of 1060 cm, which is presumably due to a stretched vibration of the Ru-N-Ru bond.

Finally have magnetic susceptibility measurements at 18 ⁰ C in the complex compound [Ru ₂ N (H ₂ O) ₂ CIq ^ (NH.), Revealed that this is diamagnetic, but after ligand modification has a slight paramagnetism. This was expected due to the assumed structural formula % \ x. The complex [Ru ₂ N (H ₂ O) ₂ Cl ₈ ^ (NH ^) ₅ can be clearly detected with the help of a Debye-Scherrer diagram using Ou-K radiation and a 9 cm Debye-Scherrer camera. This resulted in the following value

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D, 1 intensity

7.8 80

7.2 100 6.6 80 5.6 20

4.3 40 4.2 40

4.0 70 3.5 60

3.4 60

2.9 40 2.8 40 2 _β 6 100 2.2 40

2.1 80 2.0 30

From the assumed structural formula it follows that steric isomers may exist, which clay the complex according to the invention differ slightly in their physical properties.

Experiments have shown that ruthenium can be obtained from aqueous acidic solutions of the invention Can electrodeposit ruthenium compound on cathodes if the ruthenium in the solution as anionic complex is present with the following gross formula:

- * ζ-.

Such baths can be made by dissolving the complex according to the invention in water and adjusting Adjust the pH value to 4 or less by adding acid. Adjusting the pH value can be done with

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«12 -

all acids take place which do not attack the complex according to the invention. For example, if the complex is " as

before, the pH can be adjusted with hydrochloric or sulfuric acid. on the other hand, the complex lies in the shape

before, the pH can be adjusted by adding hydrobromic acid.

If the pH value is too low, the ruthenium is deposited with a low cathode current yield, while "If the pH value is too high, the ruthenium precipitate is black. A further increase in the pH value results to the formation of a "brownish deposit on the cathode, which is not a metallic ruthenium. Im in general, the pH should be 0.5 "to 4, preferably 1.5" to 2.5 ". When preparing the bath, you can Ammonium salts, for example ammonium chloride or bromide, can be added to increase conductivity.

The bath usually contains 5 to 20 g / l Ruthenium. If the ruthenium concentrations are lower, the bath must be filled up more frequently. Although it is also possible to work with higher ruthenium concentrations up to the solubility limit there are no practical advantages. In addition, this increases the carry-over losses, so that operating costs increase unnecessarily. If the ruthenium content exceeds 20 g / l, the bath should be stirred will.

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For use as anodes in the electrolyte according to the invention, platinum and platinum-coated titanium anodes «,

The bath temperature is not of major importance; it is usually 50 to 70 ^° C., since the rate of deposition is lower at lower temperatures, while higher temperatures lead to unnecessary evaporation losses. In addition, it is ^{only possible to work at temperatures below 50 °} C. if the current density is kept within narrow limits, since the cathode current yield drops rapidly at current densities exceeding 1 A / dm. However, if the precipitation rate is to be low, temperatures down to room temperature can be used, but in these cases the current density should not exceed 1.5 A / dm at room temperature if good precipitation is important. At a bath temperature of 50 ⁰ C, the deposition can take place with current densities of 0.5 to 4 A / dm ² , at 70 ⁰ C with current densities of 0.5 to 10 A / dm, provided that the current densities are above 4 A / dm ² The pH of the solution is 0.5 to 1. At currents below 0.25 A / dm ² , the rate of deposition is very low, while a current density exceeding the specified maximum leads to a low yield and ultimately to an inferior precipitate. If the current density ^{does not exceed 2 A / dm 2} at 50 ^° C. or 4 A / dm ² at 70 ^° C., the cathode current yield in a bath with 10 g / l ruthenium is generally at least 75%, based on the tetravalent ruthenium »

The required bath concentration can be maintained by adding the solid ruthenium complex can be obtained. The pH value falls over time

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but can be done by adding a dilute ammonium hydroxide solution Getting corrected. If a bath has been used for a long time, its residues can become can be recovered by evaporation and cooling. The pests then become unwanted for removal Salts, for example to remove ammonium salts, washed out with ice water and for further use solved again.

The galvanic deposition with a bath containing the ruthenium complex according to the invention is carried out explained in more detail below on the basis of exemplary embodiments.

Example VI?

The test baths were prepared by dissolving the aquo-chlorine complex [Ru ₂ N (H ₂ O) ₂ ^C1 ₈ 1 ^ 4) 3 (^ above A) in water up to a ruthenium concentration of 5 g / l and 10 g / l . To increase the conductivity of each bath 5 g / l of ammonium chloride were added while the pH was adjusted by addition of hydrochloric acid 2.5 ₀ The baths were then used at 50 ⁰ C for the deposition of ruthenium on copper cathodes, previously using were provided with a thin gold coating of platinum anodes. During the experiments, the current density was changed so that the different cathode current yields and deposition rates resulted from the table below.

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JL r / 1 Ru 10 g / l Ru current
density
(A / dm ² ) Cathode
electricity
prey
W) Low
thick after.
20 min,
(Micron) Cathode
electricity
"prey
(*) Precipitation
thick after
20 min.
(Micron) 0o5
Ο 75
1.0
1.5
2.0 100
100
100
80
64 1.4
2.0
2e4
2o9
3.1 100
100
95
91 1o3
1.9
2o3
3.5 example VII:

By dissolving the aquo-chlorine complex ₂ O) ₂ Ol ₈ ] (NEL) ₅ (sample B) in water, a bath with a ruthenium concentration of 10 g / l was produced, which after adjusting the pH to 2.5 by adding hydrochloric acid to deposit ruthenium using a platinum anode on gold-plated copper cathodes. At a temperature of 50 ° C. and a current density of 1.5 A / dm, the deposition rate was 9 microns / h and the cathode current efficiency was 80-6.

Example VIII:

A bath with a ruthenium concentration of 10 g / l was prepared by dissolving the aquo-bromine complex ₂ O) ₂ Br _{8] (NH.), In water.} The pH was adjusted to 2.5 by adding hydrobromic acid. The bath was then used using platinum anodes at a temperature of 70 ⁰ O for depositing ruthenium on gilded copper cathodes. After 20 minutes, a current leakage

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te of 1.0 A / dm was a ruthenium coating with a thickness of 2.5 microns. The cathode current efficiency was close to

In tests with different bath compositions and process conditions, it was found that undesirable products can form on the anode. This happens particularly with high ammonium chloride or bromide concentrations and a low pH value as well as high anode current density. »The nature of the products deposited on the anode depends on the bath composition. For example, from baths made with the anion complex JJRu ₂ N (H ₂ O) ₂ CIqI ^ ", nitrogen trichloride and intermediate products, sometimes mixed with other compounds, separate out. The amounts of nitrogen trichloride and the other released compounds are small and tend to decompose rapidly under the specified process conditions, especially at higher temperatures

Similar conditions can arise if the electrodeposition of ruthenium takes place in baths that contain the corresponding bromine complex anion However, the nitrogen tribromide contained in the anode is unstable, so that mainly only bromine is released o

The formation of undesirable substances on the anode can be caused by the addition of sulfamic acid or a soluble sulfamate can be reduced or even completely suppressed. In some cases, the formation can be undesirable Substances at the anode also by adding other weakly reducing substances that are more compatible with the bath Substances such as ethanol,

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However, great care must be taken when selecting such reducing agents, as they can be attacked even in the bath or oxidized to form undesirable compounds. If, for example, urea is used as a reducing agent, it can happen that this enters the anion complex and forms a coordination compound with the ruthenium, displacing some ligands. Likewise, for example, ethanol can also be oxidized, namely * first to acetaldehyde and then to acetic acid, what

. should be avoided. For this reason, the use of sulfamic acid or a soluble one is advisable Sulfamate preferable. The addition of ammonium sulfamate is particularly advantageous, since the addition of sulfamic acid the pH value is lowered, which can then be readjusted by adding ammonium hydroxide must to compensate for the effect of the sulfamic acid. Sulfamates of cations that affect the bath or the Negatively affect precipitation, may of course not be used. Another benefit of a The addition of sulfamate consists in increasing the conductivity of the bath

Even small amounts of sulfamate are already very effective in suppressing formation undesirable substances at the anode, the sulfamate goes increasingly both through hydrolysis as well as lost in the way of reaction with the anode substances that form during electrolysis, the loss being proportional to the ruthenium precipitate. Preferably initially at least 10 g / l ammonium sulfamate added. Thereafter, at least 2 g of ammonium sulfamate per gram of ruthenium precipitate should be used can be added. Usually the bath

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concentration readjusted at intervals! when the ruthenium has dropped about $ 20. It is customary to add more ammonium sulfamate together add with the ruthenium complex. One to two parts by weight of ammonium sulfamate are advantageously used per part by weight of ruthenium of the added ruthenium compound introduced.

It is not necessary to initially add ammonium sulfamate in an amount that is sufficient for the ruthenium content of the bath. However, larger amounts of, for example, up to 50 g / l appear to be without disadvantageous To stay Polgen »

l Baths containing sulfamate can be used with much more fluctuating conditions than sulfamate = free baths without the formation of undesirable anode substances. In particular, baths containing sulfamate can have an acidity which falls below the pH value of 1 to, for example, 0.5 or less, although this should be avoided because of the risk of corrosion of the surfaces to be coated. In addition, a strongly acidic bath promotes hydrolysis of the sulfamate, so that more frequent additions of sulfamate are necessary. In general, the bath compositions and process conditions of the sulfamate-free baths also apply to sulfamate-containing baths. A particularly preferred bath initially contains 12 g / l ruthenium in the form of the aquo-chlorine complex [RUgN (H ₂ O) ₂ CIqI (NH ^), and 12 g / l ammonium sulfamate ; it has a pH of 1.5 to 2.0 and a temperature of 70 ^° C.

■ Example IX;

By dissolving the aquo-chlorine complex (sample A) 909821/1068

a bath with 5 g / l ruthenium was prepared in distilled water with a pH value adjusted to 2.5 to 3 by adding hydrochloric acid. The bath temperature was adjusted to 7O ⁰ C and the pH is adjusted by a further addition of hydrochloric acid to 1.5 to the second From this bath plated with platinum titanium anode at a cathode current density of 1.0 A was / dm and an anode current density of 0.2 A / dm deposited at 7O ⁰ C ruthenium on a provided with a thin gold coating cathode using. As soon as the ruthenium content had dropped to 4 g / l, the bath concentration "was readjusted periodically by adding the solid aquo-chlorine complex, while the pH was kept at 1.5 to 2 by adding dilute aqueous ammonium hydroxide" After 3 g / l of ruthenium had been deposited, the formation of nitrogen trichloride was noticeable on the anode. An addition of 10 g / l of ammonium sulfate immediately suppressed the formation of nitrogen trichloride open circuit; there was no further formation of Stickstof ftrichlorid During the further deposition of the bath at each resetting of the ruthenium concentration was 1 * g Ammoniumsulf Amat per gram of ruthenium added..

Example X:

About the use of a bath containing sulfamate To illustrate, a bath with 10 g / l ruthenium was used as an aquo-chlorine complex (sample A), the 10 g / l Ammonium sulfamate had been added at weak Bath agitation used to under the conditions given in the table below ruthenium on a using gold plated copper cathode

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to deposit a platinum-coated titanium anode, whose Surface corresponded to five times the cathode surface. The cathode current consumption was calculated on the basis of the tetravalent ruthenium.

tempera PH value Cathode Cathode Deposition door current current discharge fast-wind ( ⁰ C) 1.5-2 density prey speed 1.5-2 (A / dm ² ) (Micron / h) 70 1.0 1.0 100 7th 70 1.5-2 4.0 86 25th 70 8.0 73 40 50 1.0 86 5

No formation of nitrogen trichloride at all on the anode could be observed during the tests.

The coatings deposited using the baths of the invention are up to. about 2 to 3 microns thick. If the electrolysis is continued, surface cracks occur with greater thicknesses; in addition, with greater thicknesses, the coatings become matt and gray. If necessary, the usual organic substances can be added to the bath to reduce the tension in the coating, provided they are compatible with the bath. The high cathode-electric yield of the baths according to the invention results in essentially no evolution of gas at the cathode, so that the coatings generally have neither strips nor fittings.

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Claims (19)

International Nickel limited, Thames House, Millbank, London, S. W. 1, England claims; 1. Process for producing a complex ruthenium compound, characterized, that an aqueous solution of ruthenium chloride with a " Excess of sulfamic acid up to hydrolysis of the sulfamic acid heated and then the complex compound is separated from the solution 2. The method according to claim 1, characterized in that that the separation of the complex compound from the reaction mixture by evaporation the solution, subsequent cooling and crystallization of the complex compound takes place. 3. The method according to claims 1 and 2, characterized in that after heating the solution of ruthenium chloride and sulfamic acid min- ' at least 3 ml of concentrated hydrochloric acid per gram of ruthenium are added to the reaction solution. 4 »Process according to claims 1 to 3, characterized in that with the ruthenium chloride 4 to 9 mol. Sulfamic acid per atom of ruthenium to be heated 5. The method according to claim 4, characterized in that the aqueous solution of Ruthenium chloride and sulfamic acid from solid hydrated ruthenium chloride and 4 to 5 moles 6 sulfamic acid per atom-96 ruthenium is produced. 9 0 9 8 2 1/10 6 8 Complex ruthenium compound, the ruthenium of which as Anion complex with the gross formula is present, in which Y is a chlorine or bromine group, χ = 2, 3 or 4 and (x + y) = 10 and ζ = (5 - x). 7. Complex connection according to claim 6, thereby marked denies that χ «is 2. 8β Complex compound according to claims 6 and 7 in Form of a salt of a monovalent cation. 9 · Complex compound according to claim 6 of the gross formula where Y e is a chlorine or bromine group » 10. Complex ruthenium compound of the gross formula 11. Method of making an aquo-bromine-ruthenium Complex, characterized in that an Aquo-Ghlor complex with the gross formula reacted with hydrobromic acid and the aquo-bromine complex is separated. 12, Use of the ruthenium complexes according to the claims 6 to 10 in aqueous acidic solution as BaO for galvanic Separation of ruthenium " 13. Use of a bath according to claim 12, the pH of which is 0.5 to 4 for the purpose of claim 12 _e 909821/1068 14. Use of a bath according to claim 12, the pH of which is 1.5 to 2.5 ", for the purpose according to claim 12th 15. Use of a bath according to claims 12 to 14 » which contains 5 to 20 g / l ruthenium, for the purpose according to claim 12. 16. Use of a bath according to claims 12 to 15t which additionally contains sulfamic acid or soluble sulfamate for the purpose of claim 12. 17. Use of a bath according to claims 12 to 16, which contains ammonium sulfamate as soluble sulfamate, for the purpose of claim 12. 18. Use of a bath according to claims 12 to 17, with a temperature of 50 to 70 ⁰ O for the purpose according to claim 12. 19. Use of a bath according to claims 12 to 17 at a current density ν
Purpose according to claim 12. a current density of 0.5 "to 10 A / dm for the S09821 / 1068