There are number of methods for the synthesis of Pd(PPh3)2Cl2 from PdCl2. Which one is best among all in terms of yield and efficacy?
We obtained good yields for a similar complex using a microwave assisted synthesis.
I haven't conducted a detailed study of this compound so I can't claim that this is the 'best' method, but I have had some success simply mixing a toluene suspension of PdCl2 and 2 equivalents of PPh3 (no need to use the more soluble Na2PdCl4, or pre-making the acetonitrile or benzonitrile adducts of PdCl2).
The reaction can probably be done at room temperature, though may need heating. The idea is that the brown PdCl2 should 'dissolve' to give a yellow solution. Any remaining PdCl2 can be filtered off and the product recrystallised by concentrating the toluene solution and/or adding ethanol.
You don't mention which isomer you want (cis or trans) so I expect you are just wanting a Heck catalyst precursor, in which case it doesn't really matter. But, if you specifically want the trans isomer (which is less stable than the cis) you will need to do the reaction at room temperature or lower and add a sub-stoichiometric amount of phosphine slowly.
On a general note, for these simple metal complexes it is definitely worthwhile getting access to the book series 'Inorganic Syntheses'. This has a fairly comprehensive list of tested synthetic routes, and is fairly detailed in the experimental details:
http://onlinelibrary.wiley.com/bookseries/10.1002/SERIES2146
Pls cCheck
Molecules 2007, 12, 1438-1446
http://opus.kobv.de/ubp/volltexte/2006/687/pdf/jovanovic.pdf
Good luck!!!
Much more easy method is to dissolve PdCl2 in a chloride solution to make PdCl4-- anions, an easy way is to dissolve the PdCl2 in ethanol plus conc HCl. When you have a solution then add cyclooct-1,5-diene (COD) to make PdCl2(COD) which is insoluble in water and ethanol. Collect the COD complex and then react it in CH2Cl2 with 2 equiv of PPh3. Very mild conditions and easy in the lab.
To the CH2Cl2 soluton of the PdCl2(PPH3)2 add petrol to get the product to form a solid.
(Mark) I'm certain that the method that you outline works and is straight-forward. However, I'm not sure how needing two additional reagents: HCl (corrosive and should be used in a fumehood) and COD (a rather smelly compound), and two steps is 'much more easy' than the one-step process of adding PdCl2 and PPh3 together in toluene (or DCM if you prefer).
The problem with PdCl2 is that it is about as soluble as brick dust in water and many solvents, if you do not want to use HCl then you can use NaCl to dissolve PdCl2, it forms Na2PdCl4. But I would choose to use HCl as it does not add any more metals to the mixture.
I know that COD has a smell which some people love to hate, but the COD method is so mild that I would choose it each time.
I would say that sometimes two steps are better than one, if it is possible in one step to replace the strongly bonded ligands with weakly bonded ones then it can make the synthesis more easy.
For example if you want to react NaCp with Mo(CO)6 then it is best to make Mo(CO)3(CNMe)3 by boiling Mo(CO)6 in MeCN overnight, it then allows the Cp chemistry to be done under very mild conditions.
In my opinion, one of the easiest methods of synthesis PdCl2(Ph3P)2 is the method described in J.Inorg.Nucl.Chem. 1970, V.32 (12), 3799-3803. To melted in a water bath was slowly added triphenylphosphine palladium chloride. After completion of addition, stirred for another 5-10 minutes, then cooled and extracted with chloroform. The extract was treated with heptane. The resulting yellow precipitate was isolated on a filter and washed with hexane.
Please Mark Foreman, in which paper did you get the procedure from Na2PdCl4 and/or Pd(COD)Cl2. I have to make PdCl2(PPh3)2 and I only have Na2PdCl4 available.
Thank you.
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