The pyridine-2,6-diimine (PDI) ligand has an extensive history since its introduction in 1998. It has the ability to catalyze a number of transformations such as olefin polymerizations, hydroborations, hydrosilations, C-H bond activation, and nitrogen fixation among others. A recent report by Gilbertson et al. documents the ability of a Fe-PDI scaffold to catalytically reduce CO<sub>2 </sub>to syngas. The ability of the PDI ligand to promote these reactions is largely due to the existence of 2 low-lying π* orbitals that can act as electron reservoirs. Much of the theoretical analysis of PDI systems has used the DFT-BS approach over the past decade. The approach gives excellent geometries. It can also provide accurate descriptions of the electronic environment when the electronic structure is dominated by a single configuration. Unfortunately, the DFT-BS energetics can be ambiguous, especially when the system is expected to have significant multi-reference character and the electronic structures are less accurate. This is true of many of the intermediates present in PDI reaction cycles. In this work, fully uncontracted multi-reference Møller-Plesset perturbation theory (MRMP2) is applied to several Fe-PDI intermediates in the CO<sub>2</sub> reduction mechanism proposed by Gilbertson et al. Using a proper balanced active space, we can not only give a more robust description of the electron distributions in these systems, but we can also successfully describe their magnetic properties.

Iron pyridine-2,6-diimine (PDI) scaffolds: A new model with MRMP2

249th National Meeting (2015)

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