Synthesis and Characterization of a Sterically Encumbered Unsymmetrical 9-Borafluorene, Its Pyridine Adduct, and Its Dilithium Salt
摘要:
The reaction of 2,6-(4-t-BuC6H4)(2)C6H3Li with BH2Cl . SMe2 in hexane or Et2O solution affords the terphenyl-substituted unsymmetrical 9-borafluorene 1-(4-tert-butylphenyl)-7-tertbutyl-9-(bis-2,6-(4-tert-butylphenyl)phenyl)-9-borafluorene (1) in good to moderate yields. Addition of pyridine gives the colorless crystalline adduct 1.py. Compound 1 is readily reduced to the deep red heteroaromatic dianionic (mu (2)-eta (5),eta (5)-1-(4-tert-butylphenyl)-7-tert-butyl-9-(bis-2,6-(4-tert-butylphenyl)phenyl)-9-borafluorenyl)bis(diethyl ether)dilithium (2) with excess lithium powder in Et2O solution. Reactions of the dianionic 2 with various metal salts leads to reduction of these salts, and bright yellow 1 is recovered in essentially quantitative yields. Compounds 1, 1.py, and 2 were characterized by H-1,C-13, and B-11 NMR spectroscopy and compounds 1.py and 2 also by single-crystal X-ray diffraction.