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    I have an 11B NMR spectrum of Sodium Borohydride. It has one peak at ~-37.5 and is a quintet. Why is it split? There is only 1 boron.
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    but there are 4 B-H's.

    Mind you i'm totally **** at inorganic NMR. I thought it was gonna be a quartet since B has s = 3/2.
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    I know there are 4 B-Hs. But according to the theory I'm familiar with, there would only be one peak, since there are no adjacent 11B.
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    By doing an 11B NMR experiment you'll only see signals caused by 11B but you'll see coupling of these signals to any other NMR active nucleus i.e. not just boron. The quintet you see is the 1J coupling to the 4 equivalent hydrides. The negative chemical shift is because hydrides have quite high electron density so shield the boron nucleus from the magnetic field.

    I think you got confused by thinking in terms of 1H NMR of organic molecules. Usually the only thing in the molecule you'll see coupling to is other protons. NMR active carbon (carbon-13) isn't abundant enough to see coupling and nitrogen and oxygen are quadrupolar which won't show coupling. If you have an organic molecule with fluorine or phosphorus (both spin 1/2), however, you will see protons coupling to them.
 
 
 
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