Inhaltszusammenfassung

The reaction of bis-imine ligands, which are synthesized from diamines containing variable bridging units between the amine functions and benzaldehyde, with Fe(2)(CO)(9) leads to the formation of di- and tetranuclear iron carbonyl complexes. Either one or both imine moieties are coordinated to Fe(2)(CO)(6) fragments by a C-H activation reaction in ortho-position with respect to the imine group followed by an intramolecular 1,3-hydrogen shift reaction toward the former imine carbon atom. Mossb...The reaction of bis-imine ligands, which are synthesized from diamines containing variable bridging units between the amine functions and benzaldehyde, with Fe(2)(CO)(9) leads to the formation of di- and tetranuclear iron carbonyl complexes. Either one or both imine moieties are coordinated to Fe(2)(CO)(6) fragments by a C-H activation reaction in ortho-position with respect to the imine group followed by an intramolecular 1,3-hydrogen shift reaction toward the former imine carbon atom. Mossbauer spectroscopy on the tetranuclear complexes suggests that there are two slightly different types of iron atoms, both of which can be described in the oxidation state +1 with S = 1/2. Corresponding to this finding, the tetranuclear iron carbonyl compounds may be reduced four times. The cyclic voltammograms show that only the first two reduction steps, which appear at very similar potential, are fully reversible. The difference between these first two reduction potentials may be determined by a complete simulation of the current-voltage characteristic and is found to depend on the nature of the bridging unit between the two iron carbonyl subunits. An effective conjugation between both organometallic moieties correlates with a large difference in the reduction potentials. A similar effect is observed in susceptibility measurements. The smallest magnetic moments are determined for those compounds that show effective communication between the metal centers in the cyclic voltammograms. Obviously the spins being present in the Fe(I) compounds can undergo effective coupling through the bridging unit. Minimizing the interaction between the organometallic subunits leads to the observation of an effective magnetic moment of up to 4.84 mu(B) at room temperature, nearly exactly matching the spin-only value of four unpaired electrons. » weiterlesen» einklappen

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