ELECTRON-DENSITY DISTRIBUTIONS IN SUBSTITUTED 2,3,4,5-TETRAPHENYL-1-GERMACYCLOPENTA-2,4-DIENES STUDIED BY NMR-SPECTROSCOPY

The signals in the C-13 NMR spectra of 2,3,4,5-tetraphenyl-1-germacyci openta-2,4-dienes (R-1 = R-2 = H, Me, cyclo-C3H5, SiMe3, SnMe3, R-1 = Me, R-2 = H, Cl) were completely assigned using 2D NMR spectroscopy. T he pattern of the variation of the chemical shifts in the C-13 NMR spe ctra indicates that the effects of substituents R-1 and R-2 on the het erocycle and on the phenyl groups are of inductive rather than mesomer ic origin and include the direct through-space polarization of bonds ( field effect).