Hemilabile Proton Relays and Redox Activity Lead to {FeNO} and Significant Rate Enhancements in NO Reduction.

Incorporation of the triad of redox activity, hemilability, and proton responsivity into a single ligand scaffold is reported. Due to this triad, the complexes Fe(PDI)(CO) (3) and Fe(PDI)(CO) (4) display 40-fold enhancements in the initial rate of NO reduction, with respect to Fe(PDI)(CO) (7). Utilizing the proper sterics and p K of the pendant base(s) to introduce hemilability into our ligand scaffolds, we report unusual {FeNO} mononitrosyl iron complexes (MNICs) as intermediates in the NO reduction reaction.

Uncoupled Redox-Inactive Lewis Acids in the Secondary Coordination Sphere Entice Ligand-Based Nitrite Reduction.

Metal complexes composed of redox-active pyridinediimine (PDI) ligands are capable of forming ligand-centered radicals. In this Forum article, we demonstrate that integration of these types of redox-active sites with bioinspired secondary coordination sphere motifs produce direduced complexes, where the reduction potential of the ligand-based redox sites is uncoupled from the secondary coordination sphere. The utility of such ligand design was explored by encapsulating redox-inactive Lewis acidic cations via installation of a pendant benzo-15-crown-5 in the secondary coordination sphere of a series of Fe(PDI) complexes.

Square planar Cu(I) stabilized by a pyridinediimine ligand.

A set of distorted square planar Cu(I) complexes were synthesized and characterized utilizing the sterically encumbering pyridinediimine ligand, (iPr)PDI (where (iPr)PDI = 2,6-(2,6-(i)Pr2C6H3N=CMe)2C5H3N). The oxidation state of the Cu center(s) were elucidated to be Cu(I) with a neutral PDI ligand system based on structural, spectroscopic, and computational data.