Bis(1‐Methyl‐ortho‐Carboranyl)Borane

Abstract

The Lewis superacid, bis(1‐methyl‐ortho‐carboranyl)borane, is rapidly accessed in two steps. It is a very effective hydroboration reagent capable of B−H addition to alkenes, alkynes, and cyclopropanes. To date, this is the first identified Lewis superacidic secondary borane and most reactive neutral hydroboration reagent.

The Effect of Carborane Substituents on the Lewis Acidity of Boranes

“…To analyze the carborane substituent effects on Lewis acidity, three sets of compounds were investigated: H 2 BR, HBR 2 , and BR 3 complexes, where R is either an ortho -, para -, or meta -carborane ( o -C 2 B 10 H 11 , p -C 2 B 10 H 11 , or m -C 2 B 10 H 11 , respectively; see Figure ). The only known compounds for these are the homoleptic tris­( ortho -carboranyl)­borane ( 10 ) and the secondary borane HB­( o -CH 3 –C 2 B 10 H 10 ) 2 , where the ortho -carbon bears C–CH 3 rather than C–H for the latter. − The results are compared to the phenyl- and pentafluorophenyl-substituted variants. The computational methods that were used to assess the Lewis acidity are the hydride, fluoride, and ammonia affinity calculations, the global electrophilicity index (GEI), and LUMO energy levels .…”