[reflux]

I understand that for a 1,2 insertion of an olefin in a M-C or M-H bond to occur the M-R bond and C=C bond must be mutually cis and in the same plane.  Would this also be true for the 1,2-insertion of a M-N bond into a C=C bond?  Or can it go by a stepwise (non-concerted) proccess.  Any ideas or good reviews would be helpful.

[rkaminski]

To be honest I don't understand fully your idea. The mechanism of insertion reaction depends strongly on the reagents and conditions. For example the reaction pathway can be totally different when you use different ligands on the metal centre and so on. If you could give some picture or example I could try to find something in the literature for you.

[reflux]

Thanks.  I'm specifically concerned with the geometry of a 1,2-insertion of an alkene (C=C) into a M-N bond to create the alkyl-metal species M-C-C-N.  From what I understand the coordinated alkene and M-N bond should be cis to one another and in the same plane for the insertion to occur.  What I am curious about is if there are exceptions.  For example, if the alkene cannot align itself cis with the M-N bond can a stepwise process be operative?  Something like forming one sigma bond and then the other.

I have several reviews on 1,2-insertion but none deal specifically or in detail with this specific reaction.

[rkaminski]

No, I think, I understand, when you put a picture:) Well, it resembles me the metathesis reaction, involving this, so called, metallacyclobutane (or whatever:P).

In my opinion, if your olefin is, for example, too bulky to go near the M-N bond and "normal" mechanism cannot occur (it means that you can have formation of such metallaazacyclobutane or analogous transition state) your possibility is also unlikely because of long distance between carbon and nitrogen atoms. I suppose that in such case after coordination of olefin you will have some ligand exchange to form, I don't know, three-coordinated specie.

I will try to check it later in the literature, it's indeed an interesting problem, but you know, if there is nothing in the literature concerning this particular case it could be interesting research project;)

Is this answer satisfy you? I'm looking forward to seeing your next post about it:)

[reflux]

Thank you very much for the thorough input!  Yes I will be researching a new reaction which will test this theory.  I brought this up in my research proposal to a 4 professors earlier this week and they didn't rule it out as an impossibility.  Overall they thought the idea was good and worth quick try.  I wish I could be more specific but until I can publish my results it wouldn't be wise for me to disclose too much of my idea.  I will certainly post any links to any relevant literature that I can find however.  I am a "pure" organic chemist and am trying to learn more and more about organometallics.  Thanks for your *delete me*

[ng]

This sort of reaction is known as sigma-metathesis and can occur with lanthanide complexes.
Tobin Marks and Gary Molander have a number of examples and this is one I have to hand
K.C. Hultzsch et al J. Am. Chem. Soc., 2006, 128, 3748

[reflux]

Thank you for the paper!  I'll try to read up some more on this process.  Are there any examples of this occuring with late transition metals?