Thank you to Dominique Duguay for providing the sample for the figure.
Monday, April 28, 2008
11B COSY
Many NMR users are very familiar with the 1H COSY experiment. It is used extensively by organic chemists. Many people do not realize that the COSY method can be used for many other abundant isotopes as well. The figure below shows the 11B COSY spectrum of ortho-carborane. The data were collected with 1H decoupling and allow the complete assignment of the 11B NMR spectrum. Note that in this case, the 11B - 11B J couplings are unresolved in the 1D spectrum. Thank you to Dominique Duguay for providing the sample for the figure.
Thank you to Dominique Duguay for providing the sample for the figure.
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3 comments:
Glenn - I have recently been looking at the B-11 spectrum of a sample of o-carborane. I noticed that your B shifts are different than mine. For example, the most shielded signal with my set-up here is at ~ -15 ppm. My shifts are referenced to 15% F3B.Et2O in CDCl3 at 0 ppm, which I thought was pretty much the universal standard. Can you confirm that you have used a different chemical shift reference?
Mike
nmrfreak,
I did not take any care in referencing the spectrum as I was not interested in the chemical shift values. If my memory serves me correctly, the parameter set was set up with neat B(OCH3)3 near 0 ppm but the COSY was run using the 2H lock on CDCl3.
Glenn
March 2, 2009
The original figure in this post had positions 1 and 4 assigned incorrectly. The figure was changed to reflect the correct assignment. Thank you to Guangyu Li for bringing this to my attention and pointing out the following reference:
Siedle, Bodner, Garber, Deer and Todd, Inorganic Chemistry 13(10) p. 2321 (1974).
Glenn
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