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Beta hydride elimination is an important reaction in organometallic chemistry: enter image description here

This reaction prohibits the use of saturated alkyl halides in coupling reactions, because it can take place after oxidative insertion of the metal. Alkenyl and aryl halides don't suffer from this unwanted reaction. Why? They also contain beta hydrogens, why aren't they readily eliminated?

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    $\begingroup$ Do you think it can be because the C-H and C-M bonds on the alkene can't bend enough for the M-H interaction to occur ? $\endgroup$ – SCH Aug 31 '16 at 14:15
  • $\begingroup$ Yeah, that could be it. $\endgroup$ – RBW Aug 31 '16 at 14:29
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    $\begingroup$ In aryl it's rather simple - you'd get benzyne - can't see anything that would offset it. $\endgroup$ – Mithoron Aug 31 '16 at 15:20
  • $\begingroup$ With sp2 carbons the C-H bond is also stronger, which might be a factor. (As an aside I think metal benzyne complexes are known but perhaps not a metal hydride complexed to a benzyne... that would probably be less stable relative to the metal aryl.) $\endgroup$ – orthocresol Aug 31 '16 at 16:19
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    $\begingroup$ Theres an inherent geometric restriction if you try and beta-eliminate from an olefin- the orbitals just struggle to line up. $\endgroup$ – NotEvans. Aug 31 '16 at 16:23

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