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 [L 2 M (EtOH) 2 ](ClO 4 ) 2 [ M = Fe ( 2 ), Co ( 3 ), in good yields (82 and 85 %)]. Light green L 2 NiCl 2 ( 4 ) was obtained analogously from NiCl 2 · 6H 2 O. Hydration of 4 afforded the dark green cationic nickel(II) complex [L 2 Ni(H 2 O) 4 ]Cl 2 ( 4a ). In compounds 2 – 4 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 [L 2 Ag]NO 3 · H 2 O ( 5 ). The molecular and crystal structures of 2 , 3 , 4a , and 5 were determined by X‐ray diffraction.