Germylene , calculations

Direct spectroscopic studies and calculations of cyclic silylene-to-silene and germylene-to-germene interconversions 99IZV2027. 

It has become common to classify all molecular compounds, which fulfill the above characteristics, as carbene analogs 9,13>. As a consequence, compounds of divalent silicon, germanium, tin, and lead may be regarded as carbene-like and are therefore called silylenes, germylenes, stannylenes, and plumbylenes. In contrast to carbenes they have one property in common the energetically most favorable electronic state is the singlet 1a2 found by experiments and calculations 9). 

Spectroscopic studies and quantum-chemical calculations of short-lived germylenes, stannylenes and plumbylenes... 

Quantum-chemical calculations are employed extensively for the interpretation of experimentally observed spectra. Increasing accuracy of modern quantum-chemical methods in the prediction of spectral characteristics, geometries and energies allows one to a certain extent to fill the gaps in experimental data available for germylenes, stannylenes and plumbylenes. Therefore we review in Section X the results of quantum-chemical studies of germylenes, stannylenes and plumbylenes. 

Quantum-chemical calculations have been used to probe all the characteristic chemical reactions of CAs (at least in the case of silylenes and germylenes). The theoretical studies cover intramolecular rearrangements, insertions into 0-bonds, additions to double and triple bonds and dimerizations. Note that experimental data on the mechanisms of these reactions are still scarce and the results of theoretical studies are needed to understand the main trends in the reactivity of germylenes, stannylenes and plumbylenes. 

This review shows that despite the huge amount of information accumulated on fundamental structural, electronic and spectral characteristics of germylenes, stannylenes and plumbylenes, many gaps still exist in this area. Modem quantum-chemical calculations partially help to fill these gaps, but reliable experimental data are needed. 

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