A complete series of 5-membered heterocycles (Ph2Ge)4X with X = O, S, Se and Te has been prepared and investigated by mass spectra, 13C NMR spectra and vibrational spectra. The 13C signals of the phenyl groups in the compounds (Ph2Ge)4X were compared with the related values in the homocycle (Ph2Ge)5. Frequency values for the symmetrical and asymmetrical stretching vibrations of the units GeGeGe and