Synthesis of B/Si Bidentate Lewis Acids, -(Fluorosilyl)borylbenzenes and -(Difluorosilyl)borylbenzenes, and Their Fluoride Ion Affinities.

Herein, we report detailed studies on a series of -(silyl)(boryl)benzenes (), in which the two Lewis acid centers consisting of silicon and boron atoms are linked via an -phenylene skeleton. -(Fluorosilyl)(dimesitylboryl)benzenes and were prepared by the reaction of fluorodimesitylborane with [-(fluorodimethylsilyl)phenyl]lithium () and [-(fluorodiphenylsilyl)phenyl]lithium (), respectively. -(Difluorosilyl)(dimesitylboryl)benzenes and were also prepared by the reaction of fluorodimesitylborane with -{[di(methoxy)methylsilyl]phenyl}lithium () and -{[di(methoxy)phenylsilyl]phenyl}lithium (), respectively, and their subsequent treatment with HF·pyridine. Compounds readily capture a fluoride ion in the presence of 18-crown-6 or [2.2.2]cryptand to afford their corresponding μ-fluoro-bridged ate complexes (). The structures of were revealed by NMR spectroscopy and X-ray crystallography. DFT studies and natural bond orbital analysis of were conducted to elucidate the nature of the Si-F and B-F bonding interactions in the μ-fluoro-bridges. The fluoride ion affinities of were investigated by H NMR spectroscopy to monitor their competitive reactions. The dynamic behaviors of at variable temperatures were monitored using F NMR spectroscopy.