15N cross-polarization using the inversion–recovery cross-polarization technique and 11B magic angle spinning NMR studies of reference compounds containing B—N bonds
✍ Scribed by Christel Gervais; Florence Babonneau; Jocelyne Maquet; Christian Bonhomme; Dominique Massiot; Eric Framery; Michel Vaultier
- Publisher
- John Wiley and Sons
- Year
- 1998
- Tongue
- English
- Weight
- 326 KB
- Volume
- 36
- Category
- Article
- ISSN
- 0749-1581
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✦ Synopsis
BoraneÈammonia complexes, trialcynylborazine and N-trimethylcycloborazane were characterized by 15N and 11B solid-state magic angle spinning (MAS) NMR. They are representative of compounds containing BÈN bonds and presenting various N and B environments, either tri-or tetracoordinated. InversionÈrecovery cross-polarization (IRCP), a spectral editing technique Ðrst introduced for 13C, was extended to 15N. For all compounds, characterized by either weak or strong 15NÈ1H dipolar couplings, the polarization inversion behavior follows the theoretical equations describing the spin dynamics associated with the IRCP sequence. This technique thus proved to be an excellent tool for identifying 15N sites according to their proton environments. The isotropic chemical shift, quadrupolar coupling constant and asymmetry factor were extracted from the 11B MAS NMR spectra. However, the unusual shape of the center band was tentatively related to the presence of residual 11BÈ14N dipolar coupling, which could be possibly reduced at higher Ðelds.