Metal enolates molecular aggregates

Metal enolate solutions consist of molecular aggregates (6) such as dimers, trimers and tetramers in equilibrium with monomeric covalently bonded species (7), contact ion pairs (8) and solvent-separated ion pairs (9), as shown in Scheme 1. The nature of the metal cation, the solvent and, to a degree, the structure of the enolate anion itself may significantly influence the extent of association between the anion and the metal cation. In general, the factors that favor loose association, e.g. solvent-separated ion pairs, lead to an increase in the nucleophilicity of the enolate toward alkylating agents and also its ability to function as a base, i.e. to participate in proton transfer reactions. 

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