posted on 2024-04-11, 06:28authored byKavyasripriya K Samudrala, Manjur O Akram, Jason DuttonJason Dutton, Caleb D Martin, Matthew P Conley
Bis(1-methyl-ortho-carboranyl)borane (HBMeoCb2) is a very strong Lewis acid that reacts with the isolated silanols present on silica partially dehydroxylated at 700 °C (SiO2‑700) to form the well-defined Lewis site MeoCb2B(OSi≡) (1) and H211B{1H} magic-angle spinning (MAS) nuclear magnetic resonance (NMR) data of 1 are consistent with that of a three-coordinate boron site. Contacting 1 with O͇PEt3 (triethylphosphine oxide TEPO) and measuring 31P{1H} MAS NMR spectra show that 1 preserves the strong Lewis acidity of HBMeoCb2. 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 Cp2Hf(13CH3)2 show that the Lewis sites are capable of abstracting methide groups from Hf to form [Cp2Hf−13CH3][H313C− B(MeoCb2)OSi≡], but with a low overall efficiency.
Funding
This research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Catalysis Science program (M.P.C.; DE-SC0022203), and the National Science Foundation (C.D.M.; Award 1753025).