Notation and Structure of Enolates

Bruckner R (author), Harmata M (editor) In Organic Mechanisms - Reactions, Stereochemistry and Synthesis Chapter DOI 10.1007/978-3-642-03651-4 13, Springer-Verlag Berlin Heidelberg 2010 

It is known that the chemistry of enolates depends on the nature of the metal. Moreover, the metals are an integral part of the structures of enolates. Lithium enolates are most frequently employed, and in the solid state the lithium cations definitely are associated with the heteroatoms rather than with the carbanionic C atoms. Presumably the same is true in solution. The bonding between the heteroatom and the lithium may be regarded as ionic or polar covalent. However, the heteroatom is not the only bonding partner of the lithium cation irrespective of the nature of the bond between lithium and the heteroatom  

The latter are aggregates that also contain other lithium compounds (e. g., LiHal, LiOR or LDA). 

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