Nitrogen coordination and iron pre-catalysts Joel D. Brock, Cornell University, DMR 0936384

1. Nitrogen coordination and iron pre-catalystsJoel D. Brock, Cornell University, DMR 0936384 Intellectual Merit: New spectroscopic tools are needed to understand changes in electronic structure at the metal center in complex catalytic processes. Graduate student Chantal Stieber and colleagues combined X-ray Emission (XES) and Absorption (XAS) spectroscopies at CHESS for this purpose. In the present study, the electronic structures of four- and five-coordinate bis(imino)pyridine iron dinitrogen complexes were examined. The work shows that dissociation of a dinitrogen ligand results in measureable differences in the ligand field at the iron center. From XAS we learn that the iron oxidation state is unchanged, and transitions to ligand π* orbitals can be observed. Although XES can distinguish between 1 or 2 bound dinitrogen molecules, it cannot distinguish between the two bis(imino)pyridine iron oxidation states or electronic structures. With these analytical tools in place, progress can be made in characterizing and further developing effective alternatives to platinum-based catalysts. S.C.E. Stieber, C. Milsmann, J.M. Hoyt, Z.R. Turner, K.D. Finkelstein, K. Wieghardt, S. DeBeer, P.J. Chirik; Inorg. Chem. 51, 3770-3785 (2012). The experimental layout in the C1 hutch, showing the array of semiconductor wafers used to collect x-ray emission intensity. CHESS DMR-0936384 2012_1