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Formation of Strong Boron Lewis Acid Sites on Silica.

ABSTRACT: Bis(1-methyl-ortho-carboranyl)borane (HB^MeoCb₂) 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 ^MeoCb₂B(OSi≡) (1) and H₂. ¹¹B{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 O═PEt₃ (triethylphosphine oxide TEPO) and measuring ³¹P{¹H} MAS NMR spectra show that 1 preserves the strong Lewis acidity of HB^MeoCb₂. 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.

SUBMITTER: Samudrala KK

PROVIDER: S-EPMC10951953 | biostudies-literature | 2024 Mar

REPOSITORIES: biostudies-literature

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Formation of Strong Boron Lewis Acid Sites on Silica.

Samudrala Kavyasripriya K KK Akram Manjur O MO Dutton Jason L JL Martin Caleb D CD Conley Matthew P MP

Inorganic chemistry 20240307 11

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 H2. 11B{1H} magic-angle spinning (MAS) nuclear magnetic resonance (NMR) data of 1 are consistent with that of a three-coordinate boron site. ...[more]

PMID: 38451151

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