Synthesis and carbón-13 NMR spectroscopy of poly(pyrazol-1-YL) alkane ligands

Abstract

The carbon-13 chemical shifts and tH-13C coupling constants of twelve polypodal ligands belonging to bis(pyrazol-1-yl)- and tris(pyrazol-1-yl)-methane classes are described. The chemical shifts show high internal consistency: for instance, a previously-reported additive model predicts, with great accuracy, the chemical shift of the central sp3 carbon. Coupling constants proved to be useful tools for the assignment of pyrazole carbons. The 11( 1 H-13C) coupling of the central carbon is linearly related to the basicity of the pyrazole substitutent in tris(pyrazol-1-yl)methanes.