Farfan, Norberto published the artcileCarbon-13 nuclear magnetic resonance spectroscopy as a method to determine relative acidity of boron Lewis acids in pyridine complexes, Application of Triphenyl(pyridin-1-ium-1-yl)borate, the publication is Journal of the Chemical Society, Perkin Transactions 2: Physical Organic Chemistry (1972-1999) (1987), 771-3, database is CAplus.
Complexes of pyridine and 2-ethylpyridine with a series of boron Lewis acids have been studied using 1H, 11B, and 13C NMR. The difference in chem. shifts (Δδc-4) between the boron complex and the free pyridine were correlated with calorimetric data. The 13C data show that Δδc-4 of pyridines provides a measure of the strength of the N → B bond, thus allowing a scale of acidity for boron compounds to be derived.
Journal of the Chemical Society, Perkin Transactions 2: Physical Organic Chemistry (1972-1999) published new progress about 971-66-4. 971-66-4 belongs to pyridine-derivatives, auxiliary class Pyridine,Benzene, name is Triphenyl(pyridin-1-ium-1-yl)borate, and the molecular formula is C23H20BN, Application of Triphenyl(pyridin-1-ium-1-yl)borate.
Referemce:
https://en.wikipedia.org/wiki/Pyridine,
Pyridine | C5H5N – PubChem