SOLVATION OF INDENYLLITHIUM AND INDENYLPOTASSIUM STUDIED BY C-13 NMR-SPECTROSCOPY

Polarization of the π‐electron systems of indenyllithium (In −Li+) and indenylpotassium (In −K+), which is generally indicative of the degree and tightness of contact ion pairing, was investigated by 13C NMR spectroscopy. The effect of changing solvent is about two thirds as great for In −K+ as for In −Li+. The indenyl anion is more strongly polarized with Li+/dimethyl sulfoxide than with Li+/ammonia, whereas the reverse is observed for In −K+. Complexation of In −K+ in tetrahydrofuran (THF) by cryptand(2,2,2) results in a π‐electron distribution identical with that of In −Li+ in hexamethylphosphoramide, indicative of solvent‐ or agent‐separated ion pairs or free ions. Small but significant cation–anion interactions are observed for In −K+ in hexamethylphosphoramide and for In −N+Me4 in THF. Copyright © 1990 John Wiley & Sons Ltd.