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

Abstract

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

N‐Triazolylpropanamide – an Acrylamide‐Derived Multifunctional Ligand for the Construction of Supramolecular Hydrogen‐Bonded Networks

“…A surprising structural feature of the molecular structure of 2 is the monodentate N-coordination of the potentially multifunctional N-triazolylpropanamide ligand through the triazolyl ring. This is quite in contrast to the previously reported iron(II) complex [(NPPA) 2 Fe(EtOH) 2 ](ClO 4 ) 2 (NPPA = N-pyrazolylpropanamide), [4] which contains the closely re- The Fe-N(triazole) distance in 2 is 2.187(1) Å, which is only slightly longer than the 2.137(2) reported for [(NPPA) 2 Fe(EtOH) 2 ](ClO 4 ) 2 . [4] While the molecular structure of 2 is simple and highly symmetrical (Figure 3), the crystal structure comprises an intricate three-dimensional hydrogen-bonded network as shown in Figure 4.…”

“…[1] As part of our continuing interest in the coordination chemistry of acrylamide [2] and acrylamidebased ligands we have earlier synthesized and characterized an acrylamide-derived pyrazole ligand, N-pyrazolylpropanamide and its complexes with various transition metals such as iron, cobalt, nickel, copper, and silver. [3,4] Thus, we reasoned that the corresponding N-triazolyl derivative would represent a valuable addition to this chemistry.…”

RuCl2(PPh3)2(N‐ppa) – A Hydrogen‐Bridged Ruthenium(II) Complex of N‐Pyrazolylpropanamide

“…This is in the range of about 1650–1660 cm –1 observed in other metal complexes of the N ‐ppa ligand in which the amide oxygen is coordinated. This shift to lower wave numbers has been attributed to a decrease in the C=O bond strength upon coordination to a metal ion 3,4. Compound 1 is insoluble in common non‐coordinating solvents and in coordinating solvents the N‐ppa ligand often appears to be displaced.…”

“…In all these complexes the N ‐ppa acts as N , O ‐chelating ligand. In contrast, monodentate N ‐coordination via the pyrazolyl ring was found for the dicoordinate silver(I) complex [( N ‐ppa) 2 Ag]NO 3 · H 2 O 4…”

“…The bond angles and distances within the coordinated N ‐ppa are unremarkable. As with other complexes of the N ‐ppa ligand,3,4 intermolecular hydrogen bonding occurs. The crystal structure consists of dimers formed by N–H ··· Cl hydrogen bonds from an amide hydrogen on one molecule with a chloride on a second (Figure 2).…”