Ate complexes, formation

Grignard reagent, which favor ate complex formation in equilibrium as determined by NMR spectroscopy. The reaction tolerates ester functions. 

Of particular interest is the process shown in equation (22), in which the ( )-alkene geometry of (20) precludes intramolecular ate complex formation and hence an addition-cyclization reaction occurs to give the a-unsubstituted carbanion (21), which may be tnqrped by protonation, deuteration or alkylation. ... 

HMPA can have large effects on equilibria. Phenyllithium reacts with Diphenylmercury, Diphenyl Ditelluride, and iodobenzene in THF to form ate complexes. In THF/HMPA the ate complex formation constants are dramatically higher than in THF. ... 

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