Abstract: | Iron(III) complexes of three aroyl hydrazones, pyridoxal isonicotinoyl hydrazone (H2pih), pyridoxal benzoyl hydrazone (H2pbh), and salicylaldehyde benzoyl hydrazone (H2sbh), were synthesized and characterized. In aqueous medium at pH 7, [Fe(pih)(Hpih)]·3H2O is formed. In acidic methanol, a 1:1 ligand-to-metal complex is formed, [FeCl2(H2pih)]Cl (1), whereas in aqueous medium at low pH cis-[FeCl2(H2pih)(H2O)]Cl·H2O (2) is formed. Compounds 1 and 2 are high-spin d5 with μeff = 5.88 μB and 5.93 μB (298 K). The crystal structures of 1 and 2 show that H2pih acts as a tridentate neutral ligand in which the phenolic and hydrazidic protons have shifted to the pyridine nitrogen atoms. The co- ordination polyhedron of 1 is ‘square’ pyramidal, whereas that of 2 is pseudo-octahedral. Compound 1 is triclinic, space group P, with a = 12.704(2) Å, b = 8.655(2) Å, c = 8.820(2) Å, α = 105.42(1)°, β = 89.87(1)°, γ = 107.60(1)°, V = 888 Å3, and Z = 2; 2 is monoclinic, space group P21/c, with a = 15.358(4) Å, b = 7.304(3) Å, c = 17.442(4) Å, β = 101.00(2)°, V = 1921 Å3, and Z = 4. |