An ab initio investigation of the electronic structure of ion-pair enolates NH2COCH2Li, PH2COCH2Li, C6H5COCH2Li, C6H5SOCH2Li: The influence of the heteroatom

The electronic structures and the geometries of lithioacetamide, lithioacetylphosphine, lithioacetophenone and lithiomethyl-phenylsulfoxide have been investigated through ab initio calculations, including correlation at the MP2 level. The different coordination modes, η1O, η3 and η1C, of the lithium center have been analyzed. In lithiomethylphenylsulfoxide, there is a clear preference for an η3 coordination of the lithium towards the enolate anion, while in the other systems the η1O and η3 coordinations are almost isoenergetic. The η1C coordination is destabilized in all the systems.