NMR and X-ray investigations of model tris- and bis-pyridinium fluoroborates

Spectroscopic and structural properties of two distinctly different products of the reaction of 2,4,6-trimethylpyrylium ion (and 2,4,6-triphenylpyrylium), with triple primary amine-tris(2-aminoethyl)amine (tren)-have been isolated and identified. In the case of the first moiety, one of the products is a symmetric tris-pyridinium salt, whereas the second one has only two groups reacting towards the pyridinium salt and the third group giving 3,5-xylidine derivative. For the second ion (2,4,6-triphenylpyrylium salt), we obtained only one symmetric product-trispyridinium salt. All structures have been confirmed by NMR data in solution and the structure of the asymmetric pyrydinium salt in the solid state by single crystal X-ray analysis. The structure of symmetric salt has been confirmed by C-13 and N-15 CPMAS NMR spectra. (C) 2004 Elsevier B.V. All rights reserved.