Tuning the electronic structure and reactivity of oxidized chromium salen nitride complexes

Transition metal nitride (N3-) complexes exhibit useful reactivity towards heteroatom transfer, as well as providing valuable insight into the mechanisms of dinitrogen reduction and ammonia oxidation. Salen ligands are capable of forming complexes with a large number of metal ions in different oxidation states and are thus a versatile platform in coordination chemistry research. By incorporating salen ligands with a variety of R-group substituents at the para position of the phenolate moieties, the electronic structure and thus the reactivity of the nitride ligand can be modified. This thesis will focus on the synthesis, characterization and reactivity of Cr nitride complexes bearing modified salen ligands (R = NO2, CF3, tBu, OMe, OiPr, NMe2, and NEt2). Salen ligands are well-known for their ability to form ligand radicals upon oxidation, as opposed to metal-based oxidation. Oxidation of CrNSalNMe2 and CrNSalNEt2 yields CrV ligand radical species, whereas the other less donating R-groups yield high-valent CrVI nitride complexes. Oxidized complexes were characterized by both experimental and theoretical techniques including UV-vis-NIR spectroscopy, electron paramagnetic resonance spectroscopy, electrochemistry, and density functional theory calculations. Depending on the locus of oxidation, desirable reactivity may be observed such as C-H bond activation. The addition of exogenous ligands may further activate the nitride ligand and facilitate homocoupling or C-H bond activation pathways.