Syntheses and structural transformations of oxorhenium(V) complexes with triazine and imidazole derivatives: mixed ligand complexes with thiocyanate, 8-hydroxyquinoline and 1,10-phenanthroline

Abstract

Mononuclear oxorhenium(V) complexes [ReO(HL1 or H2L2)(PPh3)(OH2)Cl]Cl, {H2L1 = 1-(2-hydroxyphenyl)butane-1,3-dione-3-(5,6-diphenyl-1,2,4-triazine-3-ylhydrazone) and H3L2 = 1-(2-hydroxyphenyl)butane-1,3-dione-3-(1H-benzimidazol-2-ylhydrazone)}, have been synthesized by ligand exchange with trans-trichloromonooxo-bis(triphenylphosphine) rhenium(V). The reaction of a 1 : 1 mixture of either NH4SCN, 1,10-phenanthroline (1,10-phen) or 8-hydroxyquinoline (8-OHquin) and H2L1 or H3L2, with trans-ReOCl3(PPh3)2 yielded the mononuclear oxorhenium(V) complexes, [ReO(HL1 or H2L2)(PPh3) (SCN)Cl], [ReO(HL1)(1,10-phen)Cl]Cl, [ReO(H2L2)(1,10-phen)(OH2)]Cl2·H2O and [ReO(HL1 or H2L2) (8-Oquin)Cl]. Thermal studies on these complexes showed structural transformations from mononuclear into binuclear complexes. [Re2O3(HL1 or H2L2)2(PPh3)2Cl2], [Re2O2(μ-L1 or L2)2(SCN)2] and [Re2O3 (H2L2)2(1,10-phen)2]Cl2, were synthesized pyrolytically in the solid state from the respective precursor rhenium complexes. The structures of all complexes and the corresponding thermal products were elucidated using elemental analyses, conductance, IR and electronic absorption spectra, magnetic moments and 1H NMR and TG-DSC measurements. The prepared complexes and their thermal products have octahedral configurations. The ligands H2L1 or H3L2 behave as monoanionic bidentate or monoanionic tetradentate ligands towards the oxorhenium ions. The antifungal activities of the metal complexes towards Alternaria alternata and Aspergillus niger were tested and showed comparable behavior with well known antibiotics.