Synthesis and supramolecular structures of manganese complexes with N-pyrazolylpropanamide-derived ligands

Abstract

The syntheses and single crystal X-ray structures of the multifunctional acrylamide-derived ligands N-pyrazolyl-2-methylpropanamide (1,=N-ppaMe) and a mixture of 3- and 5-methylpyrazolylpropanamide (2a and 2b,=N-3Meppa/N-5Meppa), and their Mn2+ complexes are reported, as is the Mn2+ complex of N-triazolylpropanamide (3,=N-tpa). The general synthesis involves treatment of MnCl2·4H2O with the appropriate ligand in solution in the presence of triethylorthoformate as dehydrating agent. This way Mn2Cl4(N-ppaMe)2(EtOH)2 (4), [Mn(N-3Meppa)2(N-5Meppa)][MnCl4] (5), and MnCl2(N-tpa)2(EtOH)2 (6) were obtained. In 4 the N-ppaMe ligand acts as N,O-chelating ligand whose oxygens bridge the two Mn2+ ions. The ligands are also chelating in 5. In contrast, monodentate N-coordination via the pyrazolyl ring was found for 6. The molecular and crystal structures of 1, 2a, 4, 5, and 6 have been determined by X-ray diffraction. The extensive hydrogen bonding that occurs in these compounds is discussed.