Expert: Dr. Jeffery Raymond - 5/31/2010

Question
QUESTION: how can I synthesize polymer-supported triphenylphosphine in the laboratory? the type of polymer support is not important fr example it can be polyethylene or other polymers. but the reaction condtions should be mild

ANSWER: The term "polymer supported" is very vague.
Please clarify.

(examples- bound covalently, locked stericly in a film, stuck in a hyper branched region, as a biphasic material...)

I assume you want to do some sort of organometalic catalysis with the TPP, as its a quite good leaving group once bound, but I'll need more information to help here.  

Thanks.

---------- FOLLOW-UP ----------

QUESTION: In fact I want to do the Wittig reaction, but since the seperation of phosphine oxide by-product is difficult, so I want to use polymer supported triphenyphosphin which can be seperated from reaction mixture by simple filtration, I mean triphenylphosphine which is covalently bounded to a polymer.

ANSWER: Regular old tPhP will not be what you want to work with.  I have two suggestions, one that is harder, but potentially cheaper - though not by much.

1.  (strongly suggested as you don't have to make it) you can get a gram of tPhP crosslinked to DVB as a resin from fisher for about 27 USD - at least in the US... prices do vary internationally, though usually they are more expensive here and will probably be cheaper elsewhere.

fishersci.com,
product number
AC36684-0010
Acros Organics
No.:366840010

This will be SUPER easy to filter out.

If the large grit is going to be a problem, then check ACROS directly for smaller resin.  This should be the easiest.  If you want it smaller or even soluble fully, you should be able to mechanically break it down before putting it into your solvent.
This bypasses any questions regarding your method for generating your catalyst.

2.  If you want a specific functionality, you will want to use a tPhP derivative where there is two phenyl and one styryl sub (can also be purchased, making it from tPhP is nearly impossible). tPhP cant be directly bound in with out a vinyl group or -COOH sticking off one of the benzene rings.  I prefer the vinyl because then you can go with any radical polymerization you want and it will just fall into the back bone.  If you want organic solubility, make a polypropylene or polystyrene species and if you need less hydrophobic, then go PVOH.

Radical reactions can be found on this very very good website(below).  I'd start as listed and modify as needed (Never bound tPhP before, so it may require a little more time than normal due to some radicals sitting on the P=0 region for a second.)  Even if the P=O region gets linked instead of the vinyl, it should be a secondary rxn with most sticking off from the vinyl.

http://www.pslc.ws/mactest/radical.htm
and
http://pslc.ws/macrog/lab/unit1.htm

I know that the site looks a bit child like, but Macrogalleria has good, fundamental instructions that are great for non-polymer chemists dabbling in polymers.  I use it with my student constantly.

If you need more instruction than these sites provide, let me know.

If you make it your self, be sure to dry and redissolve at least once to be sure that you get all the initiator out of there and it doesnt muck up your subsequent Wittig rxn.

Good Luck!



---------- FOLLOW-UP ----------

QUESTION: Many thanx because of your answer. but the idea of free radical polymerization seems to be impossible in this case since the product of the Wittig reaction is an Alkene itself and free radicals can react with it. I am searching for a way to make polymer supported TPP in-situ, I mean I wanna do the Wittig reaction and then polymerize the Phosphine oxide derivative in the presence of the produced alkene and seperate it by simple filtration. do you think it is possible?

Answer
I do think free radical is a possibility in this case, you just need to do it first and make sure you get the initiator out of there before using the catalyst.

I think you want to put the catalyst into a polymer first, which will still maintain the functionality but will allow you to remove initiator from the polymer before going on and using catalyst.  My suggestion is not to try it in situ, but in three steps --> make/clean polymer catalyst, use catalyst, remove catalyst.  Very few polymerizations will leave your alkenes alone completely, so after the catalysts use may not be an option.

1. Perform radical polymerization on the TPP first using a vinylated version... You should then be able to dry the product, rinse away the initiator and any unreacted product.
2. Re-dissolve the polymer-tpp and use it for your reaction.  The back bone will be unreactive, but the tpp should be exposed.
3. Extract catalyst from products using filtration or solvent transfer.

This is what is done to make polymer bound catalysts for several industrial polymerizations.  Basically you make polystyrene, but make sure that your TPP has a styrene substitute on it in place of one of the benzene rings. Afterwards, you have something like what I've drawn. (see attachment).  

This is exactly the same process used to make this polystyrene-TPP copolymer.
again fishersci.com

PS-Triphenylphosphine, Diphenylphosphino-Polystyrene, Resin Type: 1% Cross-linked Poly(Styrene-Co-Divinylbenzene), Loading: Typical loading 2.2mmol/g Based on Uptake of Benzyl Bromide, Bead Size: 75 to 150µm, 100 to 200 mesh.

Again, if you can, I'd just order this.  Otherwise, using the steps above should cover you.