Synthesis and characterization of several rhenium(I) complexes of 2-acetylpyridine and ferrocenyl carbaldehyde derivatives of 2-hydroxybenzoic acid hydrazide

The rhenium(I) carbonyl halide (X = Cl and Br) complexes, [ReX(CO)3{H2(py)L2}] (1a, 1b) and [ReX(CO)3{H2(Fc)L2}] (2a, 2b), of the ligands derived from 2-acetylpyridine and ferrocenyl carbaldehyde derivatives of 2-hydroxybenzoic acid hydrazide [H2(py)L2 and H2(Fc)L2, respectively] have been prepared in good yield. The complexes have been characterized by elemental analysis, MS, IR, UV–Vis and 1H NMR spectroscopic methods and their structures have been elucidated by X-ray diffraction. The ligand forms a five-membered chelate ring but in H2(py)L2 it is Npyridine,N′-bidentate while it is O,N-bidentate in H2(Fc)L2 complexes. Reaction of complex 1a with copper(II) nitrate yields the unexpected aqua complex [Re{H(py)L2}(H2O)(CO)3] (3) where the ligand is monodeprotonated but maintains the coordination mode observed in 1a, as shown by X-ray diffraction. However, reaction of 1b with glycine yields a conformational polymorph of the original compound, 1b′. The X-ray study shows that the orientation of the O–H phenol group against the carbonyl amide group is the main difference.