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woelen
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[*] posted on 1-3-2006 at 01:17
Really colorful oxidation states of ruthenium


I have done some experimenting with ruthenium and I made a page about this with pictures of all its oxidation states in aqueous solution (+2, +3, +4, +6, +7, +8).

It is really remarkable how colorful a single element can be in all its different oxidation states.

http://woelen.scheikunde.net/science/chem/solutions/ru.html

Is there someone else here, who did some experiments with ruthenium or its salts?

I also have some dubious results. When I add sodium sulfite to the orange/brown solution of Ru(3+), then the liquid turns a deeper orange/red/brown. Is this due to some complex of Ru(3+) or is the color I put on my website not the correct one? I can post more images of the results with sulfite, but I left them out for now, simply because the results are so weird. Also, if I reduce the red Ru(IV) solution with sulfite, I get a totally different color than with reduction with zinc and then letting it oxidize again, such that any Ru(2+) is converted to Ru(3+) again.




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[*] posted on 7-6-2007 at 11:28


Woelen, how did you dissolve the ruthenium metal? By the standard method, melting with KOH and KNO3 in a silver crucible?
Or did you use a soluble ruthenium salt to begin with?

How did you generate ruthenium tetroxide? With persulfate in acidic medium?

I will soon have to make some soluble RuCl3 from the metal, and Brauer gives a procedure which involves distilling RuO4 into a solution of HCl. Evaporation of this then gives soluble ruthenium chloride, a mix of III and IV chloride.

The RuO4 is generated by bubbling chlorine into a solution of ruthenate(VI), which in turn was generated by melting Ru with KOH and KNO3.
I would like to avoid using chlorine, since it dilutes the RuO4 which aready boils at 40°C, making its complete condensation even more difficult.




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[*] posted on 7-6-2007 at 12:33


Woelen, try and make some awesome catalysts with that. Can you get triphenylphosphine?
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[*] posted on 7-6-2007 at 12:48


The best use for RuCl3 is making MMO anodes for chlorate and chlorine maufacture, which is what I need it for.
Forget the nasty PbO2 anode experiments, DSAs actually seem easy to make, you just need the chemicals.




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[*] posted on 7-6-2007 at 13:24


I dissolved the ruthenium by adding it to a solution of 7% NaOCl with some added NaOH. Household bleach with a little NaOH added could also do the trick. Just add the powdered Ru-metal to the bleach/NaOH solution and gently heat. The metal slowly dissolves, giving a dark brownish solution, which over time turns deep red/orange.



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[*] posted on 7-6-2007 at 14:17


Thanks for the info.
I have been able to dissolve Osmium powder, which is also impervious to all acids, in a solution of NaOH and sodium persulfate in water with heating, giving a dark yellow-brown solution of perosmate. Acidification would have yielded OsO4, which I did not want to create at that moment.

I hope that Ru powder will also dissolve in NaOH/persulfate, and give RuO4 upon acidification.
How did you make the RuO4, woelen?

I am going to pay 25€ per gram of Ru powder. Do you know a cheaper source, woelen?




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[*] posted on 7-6-2007 at 16:10


The only reactions I have done with ruthenium were at university where triruthenium dodecacarbonyl was used to make alkene complexes of ruthenium under UV light. We only were allowed to use 50mg in dilute solution and no colour changes really occured.



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[*] posted on 8-6-2007 at 01:32


Ruthenium and osmium, which occur naturally in association with platinum, are very rare and expensive metals, unlike iron of which they are the homologs in the periodic table of elements, and too valuable to be simply played around with and then discarded. Woelen must be very wealthy!

BTW Although Os is impervious to all acids, it is somewhat hazardous to handle, because when heated in air it oxidizes straight to the octovalent state as the volatile and toxic tetroxide, OsO4, which has a characteristic penetrating odor.
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[*] posted on 8-6-2007 at 03:52


Sidgwick reports that treatment of Ru(SO4)2 with SO2 followed by alcohol gives a blue solution with slow formation of a blue ppt thought to contain Ru(II) (this is ~50 years ago). Halo complexes of Ru(III) such as K[RuCl4] .water are reddish although there often is a unstable green form. K2[RuCl5(OH)2] and K2[RuCl5] are also red, though some have a yellow form when heated. It looks as if Ru(III) forms complexes with halide ions fairly easily.
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[*] posted on 8-6-2007 at 04:15


I have 5 grams of Ru-powder, and I paid EUR 40 for that. You do not need to be wealthy for experimenting with Ru. I only used 50 mg or so for the experiments, which are on my website. Others spend tens or even hundreds of dollars/euro's on large amount of pyrotechnical chemicals, and I think you need to be more wealthy for pyrotechnics (on a decent scale) than for the kind of experiments I do.

I obtained the ruthenium a few years ago. Since then, prices have risen considerably. At the same time I purchased 10 grams of rhenium for EUR 50 and I did not buy iridium (at that time also EUR 40 for 5 grams). Now I realize I should have bought more of these metals at that time :(. Garage chemist, I wish I could help you, but the source I had for ruthenium (http://www.smart-elements.com, personal contact with Heinrich Pniok) is currently out of stock. From the same person I had the rhenium, now the price is 4 times as high :(.

I made RuO4 vapor by acidifying the dark orange/red solution of dissolved Re-metal in bleach with HCl, adding some Na2S2O8 and heating. You can collect the escaping gas (mainly chlorine and oxygen, but with RuO4 vapor in it) by bubbling it through a tall column of water. The RuO4 dissolves, the oxygen bubbles through, most chlorine also bubbles through. A funny experiment is to put a paper tissue in the gas-stream. It becomes dark red, due to reduction of RuO4. Be very careful with the vapor, it is insanely toxic and like OsO4 is can be very damaging to the eyes (albeit slightly less so).




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[*] posted on 8-6-2007 at 05:53


Thanks for the info, it seems like RuO4 can be prepared much easier than by the method described in Brauer.
What luck for us that persulfates, once a laboratory curiosity and not used for anything except special purposes, are available easily and cheaply today. For the chemistry of the rarer platinum metals, they are a most useful tool.

My source for Ru powder is Heinrich, too (he wrote he has Ru powder when I mailed him). He wants the said price for it.
Iridium would cost 22€/g from him.

I would catch the RuO4- containing gas in a strongly cooled receiver, make a picture of the golden crystals, and then react them with HCl which forms the desired RuCl3 as a solution. RuO4 is only difficultly soluble in water (1,7g per 100ml).

I will do the dissolution and acidifcation in the absence of chloride ions, in order to prevent that much persulfate is lost by oxidation of the HCl to chlorine.

I think, for such an expensive and at the same time volatile compound it is maybe worth the money to buy some liquid nitrogen in order to cool the receiver so strongly that no RuO4 can escape.
An alternative would be to use a gas washing bottle after the receiver, which would be filled with HCl to wash out more of the RuO4.




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[*] posted on 8-6-2007 at 08:46


Wow, Woelen, I really like what you have done here! Right up my alley! I have one question, when you say that you are "reducing water" do you mean that you are reducing water to hydroxide, thus giving off hydrogen?

2 H2O + 2e- ------> 2 OH- + H2

If I could find a cheap source of ruthenium, I would love to perform these experiments!

Could you write out the reactions for synthesizing your unusual oxidation states so I can archive them in my notebook?
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[*] posted on 8-6-2007 at 08:54


My references say Ru reacts explosively with perchlorates. Maybe it could be converted directly to the chloride in HCL solution with perchloric acid or hydrogen peroxide added drop by drop?

[Edited on 6-8-2007 by Eclectic]
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[*] posted on 8-6-2007 at 10:08


@Chemophiliac: Yes, water is reduced, producing hydrogen and hydroxide ion. At somewhat lower pH, the acid is reduced to hydrogen. There are quite a few metal ions, which are capable of this, especially at high pH. E.g. when a solution of NaOH is added to a solution of TiCl3, then a very dark blue/black solid is formed, and hydrogen gas is produced by the Ti(OH)3, which forms hydrogen gas and "Ti(OH)4", better described as TiO2.nH2O.

The reaction equation for ruthenium would be: 2Ru(2+) + 2H2O --> 2Ru(3+) + 2OH(-) + H2. In the solution, shown in the picture, the following is more likely:
2Ru(2+) + 2H(+) --> 2Ru(3+) + H2

Making Ru(2+) is done by adding zinc to an acidified solution of any Ru-salt at higher oxidation state. The following page may be helpful, it contains more of the experimental setup:

http://woelen.scheikunde.net/science/chem/exps/ruthenium/ind...

@Eclectic: I have read stories of Ru-metal reacting explosively violently with chlorate, or perchlorate, in an acidic environment. Well, I tried, and these claims simply are false. Even heating to boiling does not even touch the Ru-metal. All chlorate is completely decomposed and my lungs burn of chlorine and chlorine dioxide, but the ruthenium still is laughing at me, totally unchanged after this vigorous treatment. But I finally won with a NaOCl/NaOH mix :P.




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