Ambiphilic metal-ligand activation AMLA

For a review on CMD meehanism (a) D. Lapointe and K. Fagnou, Chem. Lett., 2010, 39,1118. For a related mechanistic proposal named as ambiphilic metal-ligand activation (AMLA) (b) Y. Boutadla, D. L. Davies, S. A. Maegregor and A. I. Poblador-Bahamonde, Dalton Trans., 2009,5820. 

Concerted metalation deprotonation (CMD)/ambiphilic metal ligand activation (AMLA) lA.CMD through 6-membered transition states... 

This process is also referred to as ambiphilic metal-ligand activation (AMLA-6), where the 6 refers to a six-membered transition state. AMLA-6 and CMD, in essence, describe the same mechanism, see D. L. Davies, S. M. A. Donald and S. A. Macgregor,/. Am. Chem. Soc., 2005,127,13754-13755. 

The fundamental conclusion from this study is that the barrier to the migration of a hydrogen atom may be lowered in the presence of an intramolecular base and is, as such, related to the concerted metaUation deprotonation (CMD) [57] and ambiphilic metal-ligand activation (AMLA) mechanisms [8, 58] described by other groups. The elucidations of these processes are also excellent examples of the synergy between careful experiment and computational studies [8, 59]. Other examples of proton-shuttling-type mechanisms have been reported, with both intra- [60] and intermolecular [61] bases being shown to lower the barrier to the formation of the vinylidene complex. 

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