Carbene Analogues of Boron Stabilized by Neighboring BB Moieties: Doubly Aromatic Bishomotriboriranides

Delocalization in doubly aromatic compounds: Bishomotriboriranide 1 is the first carbene analogue of boron (a borenate ion) characterized in solution (NMR) and in the solid state (X-ray). With the 3c–2e π bond and 3c–2e π bond that involves the borenate center of 1* and the neighboring BB unit, 1 belongs to the class of doubly aromatic compounds. The (hypothetical) classical borenate 1* without these delocalizations is estimated to be about 90 kcal mol−1 higher in energy than 1 (Dur = 2,3,5,6-tetramethylphenyl).