Redox noninnocent ligands are known to be involved in altering the overall electronic nature of organometallic complexes by serving as an electron reservoir. Pyrazine(diimine) backbones in these complexes introduce enhanced π acidity over their more well-studied pyridine(diimine) analogues and open up the opportunity for functionalization of the nitrogen at the 4position of the ring. Herein we report the characterization of bischelated pyrazine(diimine) [(P z DI) 2 Fe] n+ (n = 0, 1, and 2) complexes for electronic and structural comparison to pyridine(diimine) complexes (PDI) with similar architectures. Cyclic voltammetry studies show three reductions, two of which are ligand-based and reversible. Reduction of [(P z DI) 2 Fe] 2+ (1) to [(P z DI) 2 Fe] + ( 2) and (P z DI) 2 Fe (3) gives rise to characteristic structural changes, such as imine CN bond lengthening, indicating the formation of a ligand radical, a conclusion which is further supported by electron paramagnetic resonance (EPR) and electronic structure calculations. Comparisons between the P z DI and PDI systems are highlighted. Complex 1 can be protonated at the uncoordinated pyrazine nitrogen, resulting in changes to its spectroscopic and redox properties; efforts to further functionalize the ligand are discussed.
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