Silylene-Stabilized Neutral Dibora-Aromatics with a B═B Bond.

The unprecedented silylene-supported dibenzodiboraoxepin 2 and 9,10-diboraphenanthrene complexes 6 and 8 were synthesized. The (NHSi) 2 B 2 (xanthene) [NHSi = PhC(NtBu) 2 (Me 2 N)Si:] 2 results from debromination of the bis(NHSi)-stabilized bis(dibromoboryl)xanthene 1 with potassium graphite (KC 8 ); 2 is capable of activating white phosphorus and ammonia to form the B 2 P 4 cage compound 3 and H 2 N-B-B-H diborane species 4 , respectively. The thermal rearrangement of 2 affords the 9,10-dihydro-9,10-diboraphenanthrene 5 through a bis(NHSi)-assisted intramolecular reductive C-O-C deoxygenation process. Notably, the 9,10-diboraphenanthrene derivatives 6 and 8 could be generated by deoxygenation of 2 with KC 8 and 1,3,4,5-tetramethylimidazol-2-ylidene, respectively. The aromaticity of 6 and 8 was confirmed by computational studies. Strikingly, the NHSi ligand in 8 engenders the monodeoxygenation of carbon dioxide in toluene at room temperature to form the CO-stabilized 9,10-diboraphenanthrene derivative 9 via the silaoxadiborinanone intermediate 10 .