Mononuclear Low-Spin 3:1-Type Iron(II) Complexes of 4-Substituted 3,5-Di-(2-pyridyl)- and 3-Phenyl-5-(2-pyridyl)-4H-1,2,4-triazoles
Résumé
Two series of mononuclear 3:1-type iron(II) complexes have been obtained by the reaction of Fe(ClO4)2·6H2O with nine previously reported 1,2,4-triazole-based ligands. The first series, [FeIILS3](ClO4)2·nH2O, is based on symmetrical 4-substituted 3,5-di-(2-pyridyl)-4H-1,2,4-triazoles where LS = medpt [4-methyl-3,5-di-(2-pyridyl)-4H-1,2,4-triazole], ibdpt [4-isobutyl-3,5-di-(2-pyridyl)-4H-1,2,4-triazole], pmdpt [4-(4-methylphenyl)-3,5-di-(2-pyridyl)-4H-1,2,4-triazole], pydpt [3,5-di-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole] and pldpt [3,5-di-(2-pyridyl)-4-(1H-pyrrol-1-yl)-4H-1,2,4-triazole] whereas the complexes of the second series, [FeIILU3](ClO4)2·nH2O, incorporate unsymmetrical 4-substituted 3-phenyl-5-(2-pyridyl)-4H-1,2,4-triazoles with LU = meppt [4-methyl-5-phenyl-3-(2-pyridyl)-4H-1,2,4-triazole], ibppt [4-isobutyl-3-phenyl-5-(2-pyridyl)-4H-1,2,4-triazole], pmppt [4-(4-methylphenyl)-3-phenyl-5-(2-pyridyl)-4H-1,2,4-triazole] and pyppt [3-phenyl-5-(2-pyridyl)-4-(4-pyridyl)-4H-1,2,4-triazole]. The complexes have been investigated by 1H NMR spectroscopy and found to be in the low-spin state at room temperature. Single crystal X-ray diffraction studies of the complexes [FeII(pmdpt)3](ClO4)2·MeCN·0.5H2O (I), [FeII(ibdpt)3](ClO4)2·2H2O (II) and [FeII(ibppt)3](BF4)2·1.34MeOH·0.16H2O (III) have revealed meridional arrangements of the ligands and distorted octahedral FeN6 coordination environments about the respective low-spin iron(II) centres.
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