Theoretical study of addition reactions of carbene, silylene, and germylene to carbon nanotubes

A theoretical study of the mechanism of the reaction of a single-walled carbon nanotube (SWCNT) with carbene (H2C), silylene (H2Si), and germylene (H2Ge) has been carried out using a two-layered ONIOM(B3LYP/6-311G∗:PM3) approach. The main findings are as follows: (1) The computational results based on the method used in this work are in good agreement with recent theoretical findings [Angew. Chem. Int. Ed. 41 (2002) 1853]. That is, SWCNTs with H2C, H2Si, and H2Ge addends favor opened structures rather than three-membered rings. (2) The greater the atomic number of the carbene center, the larger the activation energy and the less exothermic (or the more endothermic) the cycloaddition reaction becomes. Therefore, addition to the CC bond of a SWCNT is more difficult the heavier the carbene center. (3) The theoretical observations suggest that the singlet–triplet splitting of a carbene can be used as a guide to its reactivity during the SWCNT cycloaddition process.