Bubbleplate (Hive Bee)
01-31-03 20:33
No 403031
      Rhodium Chloride Wacker?  Bookmark   

I did use the FSE, but didn't see any references to this patent: US4085145:
http://l2.espacenet.com/dips/viewer?PN=US4085145&CY=gb&LG=en&DB=EPD
It describes a Wacker using Rhodium Chloride instead of Palldium Chloride, no H2O, and Isopropanol for increased selectivity of desired compounds.
Any comments?
 
 
 
 
    Rhodium
(Chief Bee)
01-31-03 21:43
No 403055
      Interesting, but is it practical?  Bookmark   

Is there any obvious advantage to RhCl3 over PdCl2 warranting its higher price?
 
 
 
 
    Aurelius
(Hive Addict)
01-31-03 22:13
No 403070
      Rhodium  Bookmark   

how much more expensive?  how watched is PdCl2 (and other useful Pd compounds, such as the acetate)?  depending on how much more expensive the Rh route could be ok.
 
 
 
 
    Kinetic
(Hive Bee)
02-01-03 00:04
No 403095
      Re:  Bookmark   


how much more expensive?


About 2.7 times more expensive, according to my calculations (ouch).

Most likely putting it out of reach considering the already high cost of PdCl2. Admittedly I haven't checked the mole ratios, but 5g RhCl3.xH20 will cost around 600. Still, there is never any harm in posting new methods; somebee may have access to plenty of the stuff, and when PdCl2 becomes unavailable, we'll have to find some other way!

By the way, it's the 200th anniversary of Rhodium's discovery next year. I hope you have something special planned, as I've just noticed it's the same for both Osmium and Palladium too! See http://www.outfo.org/science/chemistry/elements/listing/discovery_year.html smile

 
 
 
 
    Bubbleplate
(Hive Bee)
02-01-03 02:30
No 403133
      Looking at the Patent  Bookmark   

it "seems" like the reaction with Rhodium chloride in Isopropanol has better yield than Pd in Methanol.

Rhodium and Palladium were discovered by William Hyde Wollaston only 200 years ago:

History

William Hyde Wollaston discovered rhodium in 1803-4 in crude platinum ore from South America rather soon after his discovery of another element, palladium. He dissolved the ore in aqua regia (a mixture of hydrochloric and nitric acids), neutralized the acid with sodium hydroxide (NaOH), and precipitated the platinum by treatment with ammonium chloride, NH4Cl, as ammonium chloroplatinate. Palladium was then removed as palladium cyanide by treatment with mercuric cyanide. The remaining material was a red material containing rhodium chloride salts from which rhodium metal was obtained by reduction with hydrogen gas.

Properties

Rhodium metal is silvery white. Rhodium has a higher melting point and lower density than platinum. It has a high reflectance and is hard and durable. Upon heating it turns to the oxide when red and at higher temperatures turns back to the element. It is a major component of industrial catalytic systems.

Sources

The industrial extraction of rhodium is complex as the metal occurs in ores mixed with other metals such as palladium, silver, platinum, and gold. Sometimes extraction of the precious metals such as rhodium, platinum and palladium is the main focus of a particular industrial operation while in other cases it is a byproduct. The extraction is complex because of the other metals present and only worthwhile since rhodium is the basis of very important catalysts in industry.

Preliminary treatment of the ore or base metal byproduct is required to remove silver, gold, palladium, and platinum. The resulting residue is melted with sodium bisulphate (NaHSO4) and the resulting mixture extracted water to give a solution containing rhodium sulphate, Rh2(SO4)3. The rhodium is precipitated out as the hydroxide by addition of sodium hydroxide, NaOH, and redissolved in hydrochloric acid, HCl, to give H3RhCl6. This is treated with NaNO2 and NH4Cl to form a precipitate of the rhodium complex (NH4)3[Rh(NO2)6]. Dissolution of the precipitate in HCl gives a solution of pure (NH4)3RhCl6. Evaporation to dryness and burning under hydrogen gas gives pure rhodium.

Guess that's why it's so expensive!
 
 
 
 
    Bubbleplate
(Hive Bee)
02-03-03 18:06
No 404021
      Interesting and Maybe Practical!  Bookmark   

SWIM just checked with his supplier. Rhodium Chloride can be had for about $18 a gram in 5 gram lots. The price goes down from there in bigger qty.