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Boron NMR

PHYSICAL PROPERTIES
 

Isotope
Natural 
Abundance
(%)
Nuclear
Spin
(I)
Magnetogyric
ratio
(107*rad/T*s)
Quadruple 
moment
(1028*Q/m2)
Resonance
frequency
(MHz)
at 11.744T
(500 MHz for 1H)
Relative 
sensitivity
(1H=1.00)
Absolute 
sensitivity
(1H=1.00)
10B
19.58
3
2.875
8.5*10-2
53.732
1.99*10-2
3.93*10-3
11B
80.42
3/2
8.584
4.1*10-2
160.419
0.17
0.13

APPLICATION FIELDS

11B NMR spectroscopy has been largely used in the boron chemistry (borane, borates, carboranes, polyhedral boranes ...) ( 93ACSR109 )
NMR REFERENCES
A typical reference sample is BF3.OEt2 (absolute frequency of 32.084 MHz with respect to 100.00 MHz).
NMR PARAMETERS
Some interesting features of B nuclei are:
  • 11B NMR is preferred over 10B NMR.
  • 11B chemical shift range between +100 and -120 ppm.
  • nJ(11B,X)=3*nJ(10B,X)
  • Both 11B and 10B are quadrupolar nuclei and the quadrupolar relaxation mechanism is often the dominant one of these nuclei. Thus, the boron NMR signal is usually broad (>10Hz).
  • Short T1 values (10-2-10-3 s for 11B) except in symmetrical environments.
  • 1J(11B-11B)=10-60Hz and 1J(11B-1H)=40-160Hz in polyhedral boranes.
  • NMR EXPERIMENTS
    In boron-containing compounds the following experiments can be helpful:
    BIBLIOGRAPHY
    An excellent review on Boron NMR can be found in 96ENC1002 . More information in 00ENC691 .

    88AR61 , 88AR204