Flash Communication: Stopping the Movement of Carbon Atoms Traveling in Organic Molecules by Pinacolboryl Substituents

When all substituents of bis(cyclopentadienyl)titanacyclopentadienes 5 are primary alkyl groups, coupling of a Cp ligand and the diene moiety in 5 gave dihydroindenyl titanium complexes 2. The intermediate complexes 1 were not obtained because complexes 2 are more thermodynamically stable than complexes 1 as previously reported. To prevent this further transformation, the influence of the bulkiness of the substituents was investigated. Pinacolboryl (Bpin) groups as substituents R¹ were found to be a key factor in disturbing the further transformation of complex 1 to 2. Complex 1 bearing Bpin substituents as R¹ was confirmed by NMR. Its dihydroindenyl moiety was removed from the titanium and converted to a TCNE-adduct to verify the structure by X-ray diffraction.