Perfluoropyridine as an Efficient, Tunable Scaffold for Bis(pyrazol‐1‐yl)pyridine Copper Complexes

This report details the syntheses of five new 2,6‐bis(pyrazol‐1‐yl)pyridine ligands carried out by a unique strategy of utilizing pentafluoropyridine for the pyridine core. Formation of each ligand is accomplished under mild conditions utilizing carbonate bases. Each ligand reacts readily with copper(II) triflate to form the corresponding salt in high yield. Ligands and complexes were characterized by a combination of multi‐nuclear NMR, FTIR, UV/Vis, and single‐crystal X‐ray diffraction. Copper(II) triflate complexes demonstrating additional coordination modes of this multi‐pyrazole ligand system were also obtained. Despite the electron withdrawing nature of fluorine, the coordination parameters of the new complexes are comparable to previous pyrazole‐based complexes. This synthetic methodology provides efficient entry to a previously difficult to access ligand system. Functionalized bis(pyrazol‐1‐yl)pyridine ligands were synthesized via a 2‐step process, utilizing pentafluoropyridine as a pyridine scaffold. The reported method provides ease of control to all substituents, and proceeds under metal‐free, mild conditions. The resulting ligands were further utilized in the formation of copper(II) triflate complexes.