Small molecule activation on heterogeneous surfaces or by enzymes in nature is believed to occur at polynuclear reaction sites. The utility of this design exploits the expanded redox reservoir afforded by multiple metal centers to act upon substrates and stabilize reactive intermediates. Hexadentate ligands can be utilized to isolate tri- and hexanuclear clusters that exhibit reactivity towards small molecule substrates and possess interesting electronic structures. To direct the formation of larger polynuclear architectures, we have developed a tris(2-aminoethyl)amine-based heptaamine ligand platform (HTrenH9) for the formation of discrete higher nuclearity clusters. Metallation of HTrenH8 in the presence of various phosphines with an organometallic FeII metal precursor affords octanuclear iron clusters of the form (HTren)2Fe8(PR3)2, which feature five crystallographically distinct coordination environments within the cluster core. Electrochemical data showcases multiple reversible redox events and two oxidation states can be chemically isolated. The electronic structure of these redox isomers has been probed by zero-field 57Fe M�ssbauer spectroscopy, SQUID magnetometry, and electron paramagnetic resonance spectroscopy. Efforts to modulate the ancillary phosphines to alter the reactivity and spin-state of the clusters will also be discussed.

Synthesis and characterization of well-defined high-spin octanuclear iron clusters

248th National Meeting (2014)

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