Nuclear magnetic resonance spectra of carbanions. Part 10. Dibenzyl-barium, -strontium, and -calcium

Abstract

1 H and 13C n.m.r. spectra of three benzyl alkaline earth metal compounds were measured and compared with those of other benzyl compounds. Their aromatic proton resonances are substantially upfield from that of benzene. This higher shielding shift is characteristic of benzyl carbanions. Chemical shift considerations indicate that the carbon–metal bonds of the benzyl carbanions in tetrahydrofuran increase in ionic nature as the counterion varies in the order of magnesium, calcium, strontium, lithium, barium, and potassium.