Synthesis And Reactivity Of Dicobalt And Diiron Complexes Supported By Binucleating Ligand Scaffolds

Homogeneous complexes have long been used to model and understand both biological and heterogeneous systems. Binucleating ligand scaffolds incorporating more complex design principles that may more accurately represent these phenomena have had a recent resurgence. In this dissertation we discuss the use of two binucleating ligand frameworks that support dicobalt and diiron complexes. The first system, a bis-pyridyldiimine (3PDI2) macrocyclic ligand was used to support a variety of redox-related dicobalt complexes that showed a propensity for strong bond activations on small molecules. The products of these bond activations often had unique binding modes, which may be used to engender future interesting reactivity. In chapter 2, we discuss the C-C bond cleavage of acetonitrile by a dicobalt macrocycle under reducing conditions. The isolated μ-CN and μ-CH3 represent unusual structures in their respective classes. The cyanide features a rare, bent binding mode due to the ligand-imposed constraints and the methyl is the first crystallographically characterized dicobalt μ-CH3 reported, to our knowledge. Oxidation and dimerization of the μ-CN complex lead to two different CN binding modes, highlighting the versatility of the ligand scaffold. In chapter 3, a reduced variant of the dicobalt complex can activate a wide variety of substrates: from H2 and CO2 to N2O and tellurium. The products of these substrate activations were characterized and discussed in context of their binding modes and the ability of the redox active ligand to facilitate the initial reactivity. In chapter 4, a tren-based ligand underwent a C–H activation under reducing conditions to yield a stacked diiron complex. This complex and its one-electron oxidized congener were studied by X-ray crystallography, NMR, IR, UV-vis, Mössbauer, and computationally. Finally, S atom insertion into the Fe–Fe bond was explored. Through redox activity or hemi-liability, both ligand scaffolds helped facilitate reactivity for these potent bimetallic complexes.