Iron(II) Bis-α-Benzyldioximate Complexes with 3- and 4-Pyridine Hemiacetals as Axial Ligands: Synthesis, Structure, and Physicochemical Properties

Resumo

The coordination compounds [Fe(DfgH)₂(HL¹)₂] and [Fe(DfgH)₂(HL²)₂], where DfgH = is the α-benzyldioxime monoanion, HL¹ = 3-pyridine hemiacetals: methoxy(pyridin-3-yl)methanol (I), ethoxy(pyridin-3-yl)methanol (II); HL² = 4-pyridine hemiacetal: methoxy(pyridin-4-yl)methanol (III), ethoxy(pyridin-4-yl)methanol (IV), and propoxy(pyridin-4-yl)methanol (V), were synthesized and studied by X-ray diffraction and IR and Mössbayer spectrosopy. According to X-ray diffration data (CIF files CCDC 1578217–1578221 for I–V, respectively), all of these Fe(II) complexes are molecular. The metal coordination polyhedron is an octahedron formed by four equatorial nitrogen atoms of two monodeprotonated α-benzyldioxime residues coordinated in the bidentate chelating fashion and by two axial nitrogen atoms of two neutral 3- or 4-pyridine hemiacetal molecules coordinated in the monodentate fashion. The DfgH^– ligands in complexes I–V are joined by intramolecular O–H···O hydrogen bonds to form a pseudomacrocyclic system. The ligands HL¹ and HL² are generated in the reaction of the corresponding alcohols with 3- or 4-pyridinecarboxaldehyde. The IR and Mössbauer spectra of the products were studied. The Mössbauer spectral parameters of compounds I–V correspond to low-spin iron(II) ions.