Vibrational spectra and ab initio analysis of tert-butyl, trimethylsilyl, trimethylgermyl, trimethylstannyl and trimethylplumbyl derivatives of 3,3-dimethylcyclopropene. XI. Secondary periodicity

Regularities of changes in the structural parameters and vibrational wavenumbers for certain moieties of the title compounds are presented. The optimized geometrical parameters and the force fields of the di- and monosubstituted 3,3-dimethylcyclopropenes were determined at the HF/3-21G* and HF/DDAll pseudopotential levels, respectively. These theoretical levels were chosen because of peculiarities of Gaussian 03 suite of programs for the Sn and Pb atoms. The theoretical vibrational wavenumbers were calculated using the corresponding scaled force fields. The regularities obtained in the form of zigzag lines for the properties as a function of the period number of X in the Mendeleyev Periodic Table are analogous to regularities that are characteristic of properties of the atoms of the 14 (IVA) group. This is known as the secondary periodicity phenomenon.