Borabenzene Derivatives. 33. 3,5-Dimethylborabenzene 1,3,4,5-Tetramethylimidazol-2-ylidene: The First Carbene Adduct of a Borabenzene1

The stable carbene 1,2,3,5-tetramethylimidazol-2-ylidene forms an adduct with 3,5-dimethylborabenzene. This adduct 8 can readily be made from the carbene and 1-chloro-3,5-dimethyl-2-(trimethylsilyl)-1,2-dihydroborinine ( 6 ) as colorless crystals. The structure of 8 is closer to that of the anion in NMe 3 Ph(C 5 H 5 BMe) ( 9 ) than to the structures of known betainic adducts. There is no noticeable conjugation between the borabenzene and the imidazol-2-ylidene moieties.