N-Pyrazolylpropanamide - a Versatile Ligand for the Construction of Supramolecular Hydrogen-Bonded Frameworks

The syntheses and single-crystal X-ray structures of several first-row transition metal complexes containing the multifunctional acrylamide-derived ligand N-pyrazolylpropanamide (1 = L) are reported. The general synthesis involves treatment of appropriate transition metal salts with an excess of 1 in ethanolic solution in the presence of triethylorthoformate as dehydrating agent. This way the perchlorates of iron(II) and cobalt(II) afforded the complexes [L2M(EtOH)2](ClO4)2[M = Fe (2), Co (3), in good yields (82 and 85?%)]. Light green L2NiCl2 (4) was obtained analogously from NiCl2 center dot 6H2O. Hydration of 4 afforded the dark green cationic nickel(II) complex [L2Ni(H2O)4]Cl2 (4a). In compounds 24 the N-pyrazolylpropanamide acts as N, O-chelating ligand. In contrast, monodentate nitrogen coordination via the pyrazolyl ring was found for the dicoordinate silver(I) complex [L2Ag]NO3 center dot H2O (5). The molecular and crystal structures of 2, 3, 4a, and 5 were determined by X-ray diffraction.