Formation of a Hybrid 1-Bora-3-boratabenzene Heteroarene Anion Derivative.

The B(C 6 F 5 ) 2 -substituted borole 2⋅SMe 2 was obtained from the phenyl bis(trimethylsilylethynyl) borane SMe 2 adduct (1⋅SMe 2 ) by a synthetic sequence containing a rare 1,1-hydroboration reaction. Subsequent thermolysis at 50 °C converted it to the bicyclic borenium/borate zwitterion 3⋅SMe 2 . Photolysis of 3⋅SMe 2 gave the diboracyclohexadiene derivative 4⋅SMe 2 , which after ligand exchange with N,N-dimesitylimidazolylidene and deprotonation gave the 1-bora-3-boratabenzene anion derivative as its potassium salt 6. Some unique follow-up reactions of the unsaturated diboron containing six-membered heterocycles were investigated.