Tris(5,6,7,8-tetrafluoronaphthalen-2-yl)borane, a Partially Fluorinated Boron Lewis Acid with Fluorination Distal to the Boron Atom

Typical congeners of the boron Lewis
acid tris­(pentafluorophenyl)­borane,
B­(C6F5)3, are fluorinated at the
aryl groups directly attached to the boron atom. The chemistry of
related electron-deficient boranes with fluorination distal to the
Lewis acidic center is largely unexplored. The preparation and characterization
of tris­(5,6,7,8-tetrafluoronaphthalen-2-yl)­borane are reported. It
serves as a model system that provides sites for further substitution
at C-1 and C-3 of the naphthalen-2-yl units. A Gutmann–Beckett
analysis of its Lewis acidity revealed that, despite remote fluorination,
it is as Lewis acidic as B­(C6F5)3. The new Lewis acid performs equally well in CO and CN
reduction as well as dehydrogenative Si–O coupling involving
Si–H bond activation. Adducts with water and a phosphine oxide
are crystallographically characterized.