Professor
Vice Chair
Hamilton Hall 551/648
402.472.3502
tageorge@unlserve.unl.edu

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Current Research
We are interested in synthesizing high-valent iron complexes. High-valent iron is found at the heart of many enzymes capable of functionalizing hydrocarbons. Typically, these reactions involve very reactive and thus unstable species with a Fe=O functional group.

Synthesizing small, stable inorganic complexes containing a Fe=O functional group and studying its reactivity is one of our current goals. Recently, we have synthesized a series of stable Fe⁴⁺ complexes. For example, the diamagnetic, trigonal bipyramidal iron(IV) complex, FeCl(PS₃), where PS₃H₃ = P(C₆H₃-3-Me₃Si-2-SH)₃, with a tripodal, tetradentate tristhiolatophosphine ligand is shown below. The proligand PS₃H₃ is also shown below to emphasis its ability, once deprotonated, to act as a tetradentate ligand. Similar complexes have been prepared with Br, I, CN and NCS in place of Cl. The ability of the three sulfur atoms to pi-bond to iron in a trigonal planar arrangement appears to be the key factor stabilizing these complexes. The chemistry of these complexes is actively being studied.

Tin analogues of the iron(IV) complexes have been prepared. These complexes have the same tetradentate ligand and a phenyl group in the fifth coordination site. These complexes are able to transfer the entire ligand to another metal. For example, the reaction of PhSn(PS₃) with FeCl₃ resulted in the formation of the iron(IV) complex FeCl(PS₃), in one step.

A different class of complex consisting of two iron atoms and two of the tetradentate ligands is shown below. The six Me₃Si groups are omitted for clarity. Each iron is in the 3+ oxidation state. The molecule is diamagnetic at room temperature suggesting antiferromagnetic coupling between the iron atoms. Each ligand intimately wraps around both iron atoms. This molecule can be oxidized by one electron to give a mixed-valence iron(III)-iron(IV) complex, and reduced by one electron to give a mixed-valence iron(III)-iron(II) complex. The magnetic and optical properties of this class of complex will be studied in the future, together with complexes containing two different metals.