Bis(μ-alkoxo)-bridged Dinuclear Iron(III) Complexes of Pyrazole-based Ligands as Models for Iron-oxo Proteins
The synthesis and characterization of two new bis(μ-alkoxo)-bridged dinuclear iron(III) complexes with the ligands 1-(2-hydroxyethyl)-pyrazole (Hnhep) and 1-(2-hydroxyethyl)-3,5-dimethylpyrazole (Hnhed), [Fe(nhep)Cl2(EtOH)]2 (1) and [Fe(nhed)Cl2]2 (2) are reported. The crystal structures of both complexes reveal the presence of centrosymmetric dinuclear units. In compound 1, the iron(III) center has a coordination number of six, with a slightly distorted octahedral geometry. In compound 2, the bulkier nhed ligand, with methyl groups at the 3- and 5-positions of the pyrazole ring, leads to a coordination number of five at the iron(III) center in a distorted square pyramidal geometry. The magnetic properties of both complexes have been investigated in the range 2-300 K and indicate the presence of fairly weak antiferromagnetic exchange interactions between iron(III) ions (J1 = −10.04 cm−1 for 1 and J2 = −12.5 cm−1 for 2). The inactivity of both complexes in the cyclohexane hydroxylation appears to be partly due to the presence of the strong iron(III)-chloride bond that does not allow exchange with the reactant molecules.
S. Tanase et al., "Bis(μ-alkoxo)-bridged Dinuclear Iron(III) Complexes of Pyrazole-based Ligands as Models for Iron-oxo Proteins," Polyhedron, Elsevier, Jan 2005.
The definitive version is available at http://dx.doi.org/10.1016/j.poly.2004.07.026
Dutch economy, ecology, and technology program
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