Derivate des Imidazols, VI. Stabile Carben-Borane

Stable imidazol-2-ylidene-borane adducts 8 and. 9 are obtained from 1,3,4,5-tetraalkylimidazol-2-ylidenes 7 and Me2S . BH3 or Et2O . BF3. An X-ray structure analysis of 8b has been performed. An ab initio calculation [MP2(fu)/6-31G**] reveals a low energy difference between two rotamers. The bond orders of the cyclic bonds imply only a minor pi interaction between the N-C-N and the C-C fragment.