Germylenes theoretical studies

The nature of substituent effects on the position of absorption maxima corresponding to n — p transition in polyatomic silylenes have been considered in detail in theoretical studies of Apeloig and coworkers126 128. Unfortunately, there is no similar study for germylenes, stannylenes or plumbylenes. However, the available experimental data show that the main conclusions obtained by Apeloig and coworkers are also applicable to polyatomic 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. 

There are examples of electron-deficient divalent metal derivatives called heavy analogs of carbene with the general formula R2M , including silylenes, "" germylenes, "" " stannylenes, "" "" and plumbylenes. When compared to carbenes, however, these compounds exhibit a significantly decreased reactivity in C-H insertion reactions. Theoretical studies have indicated that the heavier the metal, the larger the activation barrier and the less exothermic the reaction. Electropositive substituents, however, may increase reactivities. " ... 

A theoretical study of the reaction of germylene (H2Ge ) with isocyanic acid (HNCO) by DFT has been reported in a Chinese journal and predicted the product to be H3GeNCO.i ... 

Silicon and germanium also exhibit carbene-like chemistry. A review comparing carbene and silylene chemistry was published. All the examples of germylene chemistry are from theoretical studies of their structure and their interaction with alkenes. A practical demonstration of silylene chemistry was reported. Ab initio calculations have been performed on the addition of silylenes to alkenes and they shed new light on the presence of intermediates, the structure of the transition state and the effect of substituents. ... 

Theoretical study of cycloadditions of formaldehyde with cyclopropyhdene, dimethyl-silylene carbene, and dichloro-germylene carbene has been conducted at MP2/6-311-t-G and MP2/6-31G levels of theory two competitive dominant pathways have been identified in each case. Likewise four competitive dominant pathways have been found for reaction of dichlorogermylene silylene and acetaldehyde. ... 

Experimental aspects of the dimerization of germylenes, stannylenes and plumbylenes were discussed in a review363. Relations between the characteristics of ER2 (E = C, Si, Ge, Sn, Pb R = H, F) and the structure of their dimers E2R4 were studied theoretically by Trinquier and coworkers364-367. 

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