Coordination complexes of hexadentate phthalazine hydrazone ligands

Wen, Tao (1988) Coordination complexes of hexadentate phthalazine hydrazone ligands. Masters thesis, Memorial University of Newfoundland.

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Abstract

The cobalt(II) and nickel(II) coordination complexes of three potentially hexadentate phthalazine hydrazone ligands, obtained by reacting 1,4-dihydrazinophthalazine ( DHPH ) with an appropriate aldehyde or ketone, have been investigated, in which the variable terminal donor substituents include β-methyl pyridine (PMP), pyridine (PPA) and N-methyl imidazole (PMI) groups. Studies on the analytical, -- [special characters omitted] -- spectral, X-ray, and magnetic data of the complexes reveal that the ligands are able to form double μ-bridged bimetallic complexes, in which two pseudo-octahedral metal centers are brought into close proximity by a common phthalazine diazine bridge as well as by the second either anionic [ binuclear 2:1 ( metal:ligand ) species ] or another diazine bridge [ binuclear 1:1 derivatives ]. In the binuclear 2:1 complexes three in-plane coordination sites of the pseudo-octahedral metal center are occupied by ligand nitrogen donors and the rest of the sites involve coordinated anions and water/solvent molecules. Two binuclear 2:1 chloride complexes of the ligand PMP, [Co₂(PMP)Cl(H₂O)₄]Cl₃4H₂O and [Ni₂(PMP)Cl(H₂O)₄]Cl₃4.5H₂O, have been characterized by single crystal X-ray diffraction. For the 1:1 compounds the six coordination sites are all occupied by the nitrogen atoms from two ligands. All the complexes exhibit very intense metal-to-ligand charge transfer absorption ( ε > 9200 Lmol⁻¹cm⁻¹ ) in the visible region ( 19000 - 21000 cm⁻¹ ). Variable-temperature magnetic susceptibility measurements on some complexes indicate antiferromagnetic exchange between the metal ion centers.

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