1. Purpose

This experiment demonstrates the technique used to obtain NMR spectra of ¹¹B (I = 3/2, natural abundance 80.42%). As an example we have chosen the commercially available 1,7-dicarba-closo-dodecaborane, since this compound gives a spectrum containing four different signals with rather low line-width. Furthermore, the spectrum can be recorded with or without proton decoupling; thus a spin–spin coupling ¹J(B,H) can be observed.

2. Literature

D. Reed, Chem. Rev. 1993, 109–116.
B. Wrackmeyer, Annu. Rep. NMR Spectrosc. 1988, 20, 61–203.
A. R. Siedle, Annu. Rep. NMR Spectrosc. 1988, 20, 205–314.

3. Pulse Scheme and Phase Cycle

Proton-decoupled boron-11 pulse sequence and phase cycle

4. Acquisition

Time requirement: 5 min

Sample: 100 mg 1,7-dicarba-closo-dodecaborane in 0.7 ml CDCl₃.

A multinuclear probe-head is required for the measurement of ¹¹B spectra. There are special ¹¹B probe-heads available which don't have a glass insert, thereby reducing the background signal. After tuning the multinuclear probe-head to ¹¹B on the observe channel and to ¹H on the decoupler channel, use a sample of BF₃·O(C₂H₅)₂ to detect