Tris(diphenylmethylene)methane dianion (12-), tetraphenylacetone dianion (22-), and diphenylacetate dianion (32-) were generated in dimethyl sulfoxide or tetrahydrofuran solutions by deprotonation of the appropriate carbon acid. Chemical shifts, carbon-carbon spin coupling constants, and other spectroscopic evidence indicated an sp2-hybridized central atom for all dianions, as well as D3 symmetry for the all-carbon dianion. The one-bond CC spin coupling constant for 12- (62 Hz) increased upon consecutive replacements of diphenylmethylene by the groups, i.e., to 69 Hz for 22- and 76.7 Hz for 32-, 2K+ (86.0 Hz for the Li+ salt) reflecting charge localization at oxygen. An empirical model for the residual charge on phenyl-substituted resonance-stabilized carbanions that allows comparison of dissimilarly substituted carbanions was developed.
ASJC Scopus subject areas
- Colloid and Surface Chemistry