Sciencemadness Discussion Board

Easily decomposable Pt salt from PtCl2

DrMario - 6-11-2014 at 21:32

Problem: fill a (soda lime) glass capillary with an aqueous solution of a Pt salt, heat it so that at least part of the salt decomposes and some Pt deposits on the capillary wall.

I have some PtCl2, but that is way too stable and will decompose at temperatures that the capillary can't possibly survive. So I need to synthesize another salt, starting from PtCl2, which will decompose easily.

Do you have suggestions/ideas?

gardul - 6-11-2014 at 21:57

how about Platinum(II) acetate? I've heard ( I think) very little research has been done on it.

DraconicAcid - 6-11-2014 at 23:26

Platinum oxalate should decompose nicely, but I doubt that it would be soluble. Maybe mix your platinum chloride with an aldehyde, and see if it will act like Tollen's reagent.

DrMario - 7-11-2014 at 07:48

Quote: Originally posted by gardul  
how about Platinum(II) acetate? I've heard ( I think) very little research has been done on it.


You think platinum acetate would decompose easily?

DrMario - 7-11-2014 at 07:51

Quote: Originally posted by DraconicAcid  
Platinum oxalate should decompose nicely, but I doubt that it would be soluble. Maybe mix your platinum chloride with an aldehyde, and see if it will act like Tollen's reagent.


I could make platinum oxalate easily enough. At what temp is it supposed to decompose? It doesn't _necessarily_ have to be dissolved in aqueous solution. It can be any suitable solvent.

WGTR - 7-11-2014 at 08:08

Have you already tried thermally decomposing platinum chloride? Soda lime glass can handle something between 700-750C before sagging under its own weight. Slow heating in a kiln, with the glass resting on a support, is key to achieve this temperature.

Also, do you need a platinum mirror, or just an invisible "seed" layer on the inside?

Praxichys - 7-11-2014 at 09:22

Ammonium platinum chloride (Tetraammineplatinum tetrachloroplatinate) or Cisplatin (diamminedichloroplatinum) might decompose at a lower temperature than straight platinum chloride. I can't seem to find any data on that though.

[Edited on 7-11-2014 by Praxichys]

DrMario - 7-11-2014 at 09:50

Quote: Originally posted by WGTR  
Have you already tried thermally decomposing platinum chloride? Soda lime glass can handle something between 700-750C before sagging under its own weight. Slow heating in a kiln, with the glass resting on a support, is key to achieve this temperature.

Also, do you need a platinum mirror, or just an invisible "seed" layer on the inside?


Just a seed layer, if you want to call it that way. A layer of small particles (sub-µm) is all I hope for. It almost doesn't matter how small and how few they are, since platinum is such a fabulous catalyst. Smaller would be better as the capillary itself is really narrow.

Wikipedia lists temperatures around 570C as the glass transition temp for soda lime. I am not comfortable heating such a tiny capillary at temps so much higher than glass transition. And PtCl2 is quite stable to at least 750C.

[Edited on 7-11-2014 by DrMario]

DraconicAcid - 7-11-2014 at 09:59

Quote: Originally posted by DrMario  
Quote: Originally posted by DraconicAcid  
Platinum oxalate should decompose nicely, but I doubt that it would be soluble. Maybe mix your platinum chloride with an aldehyde, and see if it will act like Tollen's reagent.


I could make platinum oxalate easily enough. At what temp is it supposed to decompose? It doesn't _necessarily_ have to be dissolved in aqueous solution. It can be any suitable solvent.


I'm not sure what temperature it would decompose at, but other metal oxalates decompose easily enough. If you're worried about how much heat it would take to melt the capillary, you'd probably be better off heating a solution of your platinum chloride with a mild reducing agent, and keeping the temp below 100 oC.

DrMario - 7-11-2014 at 10:04

I just got an idea: according to Wikipedia, platinum (II) iodide decomposes at 380C. I guess I could easily make PtI2 with a simple substitution reaction, with KI for example.

The only problem is, is PtI2 soluble in water or an alcohol? Or anything at all? I have no data on this compound.

gdflp - 7-11-2014 at 10:19

Just checked my CRC for you, platinum(II) iodide decomposes at 360°C and is insoluble in water and ether, is slightly soluble in sodium sulfite(aq), and is soluble in HI. This data might be slightly outdated as my CRC isn't new(to be honest it's a 1984 65th edition), but I've always found the data to be accurate.

DrMario - 7-11-2014 at 10:33

Quote: Originally posted by gdflp  
Just checked my CRC for you, platinum(II) iodide decomposes at 360°C and is insoluble in water and ether, is slightly soluble in sodium sulfite(aq), and is soluble in HI. This data might be slightly outdated as my CRC isn't new(to be honest it's a 1984 65th edition), but I've always found the data to be accurate.


Thanks a lot.

By "HI" they certainly mean hydroiodic acid - do they mention if it's concentrated or not? Also, I have no idea how to get pure hydroiodic acid of appreciable concentration.

Also... I am starting to have some doubts that the substitution reaction would work.

WGTR - 7-11-2014 at 10:41

Here's another idea for you.

Do you know how silver mirrors are made? After cleaning in nitric acid, soda lime glass is soaked in a stannous chloride solution. After quick rinsing, the glass is soaked in a silver nitrate solution. The stannous ion on the glass reduces the silver, leaving an almost invisible silver seed layer on the glass. This is now the basis for further silver deposition using other techniques. I've done this before, and the glass will appear to darken slightly due to the small amounts of silver on the surface. Instead of silver nitrate, gold chloride, or platinum chloride could be used.

Also, I'm not sure that PtCl2 decomposes at as high a temperature as you might think. This reference mentions the different decomposition temperatures for different platinum salts:

Attachment: Synthesis of Platinum Particles from H2PtCl6 with Hydrazine as Reducing Agent.pdf (760kB)
This file has been downloaded 380 times

When I was interested in making dye-sensitized solar cells, I looked into making platinum counter electrodes. I thought the thermal decomposition of H2PtCl6 was carried out at fairly low temperatures. After some quick checking, it turns out that all of the references that I found direct thermal decomposition to be carried out at 380C for 30-60 min on FTO conductive glass.

The following reference describes the thermal decomposition of
H2PtCl6 to PtCl2 at 350C in air, and that it can be reduced with hydrogen to Pt at 150C.

Attachment: pPLATINUM( 11) CHLORIDE.pdf (724kB)
This file has been downloaded 937 times

If reduction is needed, instead of hydrogen, alcohol vapors in an inert gas can be used. I did something like this when reducing ITO on glass:

https://www.sciencemadness.org/whisper/viewthread.php?tid=27...

[Edited on 11-7-2014 by WGTR]

gdflp - 7-11-2014 at 11:00

https://www.erowid.org/archive/rhodium/chemistry/hydriodic.h... and http://www.youtube.com/watch?v=7zC0nnQy2kE may be useful. This may or may not be legal depending on where you live. Also, I would assume concentrated acid, but I'm not sure.

gardul - 7-11-2014 at 16:29

Quote: Originally posted by DrMario  
Quote: Originally posted by gardul  
how about Platinum(II) acetate? I've heard ( I think) very little research has been done on it.


You think platinum acetate would decompose easily?



If you have the ability to heat to 200 - 300C. I don't remember the actual number. I've only have read about the substence and never have partaken in any experment with it.

zed - 8-11-2014 at 16:57

http://www.sciencemadness.org/talk/viewthread.php?tid=10670

Are you going to etch the glass first?

Might provide better purchase.

Could allow dilute PtCl2 to dry on surface of etched glass inside tube. Then melt a little NaBH4 in the tube. Cautiously.

More usual to mount the catalyst on a small piece of pumice, inside the tube.

[Edited on 9-11-2014 by zed]

DraconicAcid - 8-11-2014 at 17:53

Quote: Originally posted by zed  
Could allow dilute PtCl2 to dry on surface of etched glass inside tube. Then melt a little NaBH4 in the tube. Cautiously.


Sodium borohydride to reduce platinum(II)? That strikes me as overkill.

Texium - 8-11-2014 at 19:40

Quote: Originally posted by gdflp  
This data might be slightly outdated as my CRC isn't new(to be honest it's a 1984 65th edition), but I've always found the data to be accurate.
Nice, I have the 66th edition. Like you said, the information seems to still be good as far as I can tell.

Also, on the topic of platinum chemistry, I just went and read up on some of those complex compounds and found them quite interesting. It's too bad that platinum has to be so prohibitively expensive. Maybe some day in the distant future when I'm retired if I have the money...
It is really interesting though how little information there seems to be about these compounds on the internet. I guess a lot of it is that the companies researching the compounds (the chemotherapy related ones in particular) want to try and keep the information secret so others don't steal their discoveries. It would be interesting if we as amateurs were able to put out a more full body of research on compounds like these. Not just platinum ones, but really any obscure compounds that have not really been looked at closely, or have been but only privately.

DrMario - 8-11-2014 at 22:41

Quote: Originally posted by zed  
http://www.sciencemadness.org/talk/viewthread.php?tid=10670

[Edited on 9-11-2014 by zed]


Could you really afford more than 10 g of sodium chloroplatinate for that experiment? "Sacrifice" is the word I was going to use.

blogfast25 - 9-11-2014 at 06:40

Quote: Originally posted by DraconicAcid  
Maybe mix your platinum chloride with an aldehyde, and see if it will act like Tollen's reagent.


My experience with that, using formaldehyde on PtCl2(aq), is that it doesn't work, presumably because the Tollens' reaction takes place in basic conditions. So unless you can complex the Pt to withstand the alkaline conditions (as you do with AgNO3 by means of ammonia) aldehydes will probably NOT reduce Pt(II).

But other reducing agents like sodium metabisulphite (in acid/neutral conditions) do. Not sure whether that would mirror though.
Quote: Originally posted by zts16  
It is really interesting though how little information there seems to be about these compounds on the internet. I guess a lot of it is that the companies researching the compounds (the chemotherapy related ones in particular) want to try and keep the information secret so others don't steal their discoveries.


Simple googling will probably not be sufficient here, as much of that stuff will be behind pay walls.

[Edited on 9-11-2014 by blogfast25]

Dan Vizine - 14-11-2014 at 13:19

Interesting that you should mention that. In the late 70's and early 80's I made a lot of different platinum drugs for the NCI. I see that one of the ones I made experimental lots of is now called Carboplatin. That one stands out because we had to make the cyclobutane-1,1-dicarboxylic acid ligand. Anyway, these drugs, or cisplatin, are not the way to go.

If you want a thermal method, the diammonium hexachloroplatinate is the usual method. The results will be variable, it's not a uniform process.

You may find something in this paper that I once collected when I wanted to Pt plate some resistance heating wire.



Attachment: Electroless Pt Group Metal Plating.pdf (70kB)
This file has been downloaded 1882 times

zed - 14-11-2014 at 14:00

Umm. As those things go, Platinum isn't that expensive. It recycles well, and a single gram is a very useful amount.

About the same price as gold now. Historically, Platinum has sold for much more, in relation to Gold.

World economic problems have driven up the price of Gold. In times of unrest, folk gravitate towards Gold. Perhaps Platinum has gone along for the ride.

In 97,98,99.....Platinum was floating around at approximately 350 dollars per ounce. When things started to go sour, the price jumped.

Been some interest in Tungsten Carbide as a replacement.

[Edited on 14-11-2014 by zed]

Fleaker - 8-12-2014 at 13:16

If you want to coat the class, leave some concentrated sodium hydroxide in it til etched, rinse out the residuals mostly with DI water, elute up some chloroplatinic acid solution, then 1% v/v N2H4 solution.