Abstract
Bis(1-methyl-ortho-carboranyl)borane (HB(Me)oCb(2)) is a very strong Lewis acid that reacts with the isolated silanols present on silica partially dehydroxylated at 700 °C (SiO(2-700)) to form the well-defined Lewis site (Me)oCb(2)B(OSi≡) (1) and H(2). (11)B{(1)H} magic-angle spinning (MAS) nuclear magnetic resonance (NMR) data of 1 are consistent with that of a three-coordinate boron site. Contacting 1 with O═PEt(3) (triethylphosphine oxide TEPO) and measuring (31)P{(1)H} MAS NMR spectra show that 1 preserves the strong Lewis acidity of HB(Me)oCb(2). Hydride ion affinity and fluoride ion affinity calculations using small molecules analogs of 1 also support the strong Lewis acidity of the boron sites in this material. Reactions of 1 with Cp(2)Hf((13)CH(3))(2) show that the Lewis sites are capable of abstracting methide groups from Hf to form [Cp(2)Hf-(13)CH(3)][H(3)(13)C-B((Me)oCb(2))OSi≡], but with a low overall efficiency.