Investigations on the structure of 1-dimethylaminoallylalkali compounds
摘要:
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 thermodynamically more stable than the exo-conformation. Cryoscopic measurements indicate that the potassium compound 2 is a monomer under the experimental conditions studied here. The lithium compound 4 exhibits a monomer-dimer equilibrium that lies almost completely on the side of the dimer at higher concentrations. Ab initio calculations again support these findings. The effect of specific solvation upon the most stable conformation (eta(4)-endo-in) of both the lithium and the potassium species is investigated at the HF level of theory. (C) 1999 Elsevier Science Ltd. All rights reserved.