Dinuclear iron complexes based on parallel beta-diiminato binding sites: syntheses, structures and reaction with O2.

With the background that certain natural systems utilize two Fe(II) centres in their prosthetic groups for the activation of O2, a ligand system containing two parallel beta-diiminato binding sites linked by a xanthene backbone ([RXanthdim]2- with residues R = 2,3-dimethylphenyl and 2,4-difluorophenyl at the iminato units, respectively) was investigated with respect to its Fe(II) coordination chemistry in order to study O(2) activation reactions. Hence, the corresponding lithium salts were treated with FeCl2 to yield the complexes [Me2C6H3Xanthdim]Fe2Cl3(Li(thf)3), and [F2C6H3Xanthdim]Fe2Cl3(Li(thf)3), , respectively, each of which comprises Cl-Fe(micro-Cl)Fe-Cl(Li(thf)3) units. and indeed readily react with O2 to give the oxides [RXanthdim]Fe2Cl2O containing Fe(III)-O-Fe(III) moieties. Due to the electron withdrawing F atoms reacts more slowly than . The molecular structures of , and [Me2C6H3Xanthdim]Fe2Cl2O, , as determined by single crystal X-ray diffraction are discussed, and an investigation concerning their magnetic properties revealed an antiferromagnetic coupling of the two iron centres in all complexes; naturally, the strongest coupling is observed for .