Synthesis, Structures and Reactivity ofN-Borane-Protected 1,1′-Bisimidazoles with Different Bridging Functions

The bridging functions Me2Si, [(CH2)3(CMe2)2N]B and CH2 have been used to connect two imidazoles in the 1,1′-position. The bisimidazolyl compounds were treated with BH3 or BEt3, and the resulting N,N′-bisborane-protected products 1, 3b, 4a, and 5b were characterized by X-ray structure analyses. Reaction of 1,1′-bis(4,5-dimethylimidazolyl)methane with BBr3 yielded the macrocyclic dicationic tetraimidazolyl compound 6. The behavior of the N-protected bisimidazoles 1 and 3−5 towards deprotonating agents was investigated and it was found that 1,1′-bis(3-borane-4,5-dimethylimidazolyl)methane (5b) is deprotonated to give a dianionic dicarbene compound. Its reaction with Cp2MCl2 allowed the formation of the corresponding titanocene and zirconocene complexes 8 and 9, which were characterized by X-ray structure analyses. In 9 a 3c,2e B−H−Zr bond is present. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)