Ligand exchange processes on solvated lithium cations VI. Determination of coordination numbers by ligand substitution and 7Li NMR

Abstract

On the basis of 7Li NMR studies the coordination mode of phenantroline (phen) and bipyridine (bipy) to Li+ ions was found to be [Li(phen)2]+ and [Li(bipy)2]+ in the weakly coordinating solvent nitromethane. A large chemical shift of the 7Li signal indicated a strong interaction between the ligand and the metal center. The related sp2-hybridized N-donor ligand 2, 2′-bis[(4S)-4-benzyl-2-oxazoline] (biox) showed a negligible effect on the 7Li shift, suggesting that almost no interaction occurs between the Li+ center and biox as compared to Li+ and the solvent γ-butyrolactone. Corresponding DFT (RB3LYP/LANL2DZp) calculations have clearly indicated that the poor coordination of biox is not caused by steric effects but rather by the electronic nature of the heterocyclic biox system. © 2010 Verlag der Zeitschrift für Naturforschung.