Fertile
Bluelighter
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- Mar 31, 2022
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Above is a link to the most appropriate paper.
Wilkinson's Catalyst|Mechanism|Hydrogenation of olefins
Wilkinson's catalyst is used in selective hydrogenation of alkenes and alkynes. It is a homogeneous catalyst. Mechanism is explained.
www.adichemistry.com
Wilkinson's Catalyst - an overview | ScienceDirect Topics
Above are other examples of Wilkinson's catalyst to show the scope of it's activity. Useful for learning more about this catalyst.
Above is a decent MSDS of the catalyst.
I should add that the active compound in the hydrogenation is actually Hydridotetrakis(triphenylphosphine)rhodium(I) (CAS 18284-36-1)
Pros - well established and proven (using the latest analytical technology) mechanics. Available in a ready-to-use form, uses catalyst can be regenerated (increasing efficiency). Convenient solubility properties making separation quite simple. Non-toxic. Hydrogenation occurs > x4 faster than related rhodium catalysts. Hydrogenation oan take place in other appropriate vessels (than Parr hydrogenation units) are safe although they should be constructed of stainless steel (certain reactions need specific kinds of steel but from documentation, stainless steel is fine)
Cons - a MW of 925.22 so that the 10 molar % means that even for quite small quantities, rather a lot of catalyst is needed. Incompatible with certain materials which can result in both toxic and flammable materials.
I have struggled to find several papers which detail the mechanics of the hydrogenation. If anyone can fin them, I would be most greatful:
The crystal and molecular structure of tetrakistriphenylphosphinerhodium(I) hydride
I will conclude by noting that this catalytic technique covers a wide scope and so it finds uses all over organic chemistry. It isn't selective to N-allyl but to all allyl and propenyl groups and it can also readily reduce oxygen and is known to reduce halides. This latter is interesting as it's often quite simple to exchange a -OH for a halide BUT reduction of the -OH isn't possible and so going via the halide opens up a wide range of options.
The above detail the mechanism so on one hand they can be considered as useful but not vital... but as the old saying goes 'failing to plan is planning to fail' and so I would appreciate knowing the details to see what impurities leech into the catalyst.
I've used silver, gold and various non-metallic catalysts (such as methyl nitrite) but the cost of this catalyst means that close planning is important to know if and when the catalyst will need replacing and/or regenerating).
Any and all reference is welcome. I'm hoping someone is in the middle of their 3rd or 4th year of organic chemistry and (here I dream_ have been using Wilkinson's catalyst (or an improved alternative) and can forward the information - things I used to know in 1991 but have since slipped my mind. Didn't Einstein remark 'Never remember anything you can look u['. Well I have 'sufficient' information but who is to say someone has since discovered a vastly better alternative.
Many thanks to you all.