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Anionic lanthanide shift reagents. Application to the assignment of NH peaks of amidinium ions

✍ Scribed by Charles L. Perrin

Publisher: John Wiley and Sons
Year: 1981
Tongue: English
Weight: 264 KB
Volume: 16
Category: Article
ISSN: 0749-1581
DOI: 10.1002/mrc.1270160104

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✦ Synopsis

Anionic EDTA complexes of Pr(III) and Eu(II1) produce dowdeld and upfield shifts, respectively, of the NH resonances of amidinim ions, RC(NH2),+. These LnEDTA--induced shifts arise through the formation of weak ion pairs. Results for the acetamidininm ion show that H,, the high field NH, experiences a greater shift than HE. This result con6rms the expectation that in the ion pair the anionic shat reagent approaches closer to Hz. Thus LnEDTA--induced shifts can be used to assign NH peaks of amidininm ions. Such shifts are then used to assign the low field NH peak of the benzamidinium ion to HE, whereas the low field NH peaks of the azoisobutyramidinium ion and formamidinesul6nic acid are assigned as Hz.

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