Investigations on the structure of 1-dimethylaminoallylalkali compounds

Structural investigations (NMR) show that both 1-dimethylaminoallyllithium (4) and potassium (2) exist exclusively in the endo conformation in THF. Ab initio calculations also conclude that the endo-structure is thermodynamic ally more stable than the exo-conformation. Cryoscopic measurements indicat e that the potassium compound 2 is a monomer under the experimental conditi ons studied here. The lithium compound 4 exhibits a monomer-dimer equilibri um that lies almost completely on the side of the dimer at higher concentra tions. Ab initio calculations again support these findings. The effect of s pecific solvation upon the most stable conformation (eta(4)-endo-in) of bot h the lithium and the potassium species is investigated at the HF level of theory. (C) 1999 Elsevier Science Ltd. All rights reserved.