A new iron aziridination catalyst supported by a macrocyclic tetracarbene ligand has been synthesized. The catalyst, [((Me,Et)TC(Ph))Fe(NCCH(3))(2)](PF(6))(2), was synthesized from the tetraimidazolium precursor ((Me,Et)TC(Ph))(I)(4) and characterized by NMR spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction. This iron complex catalyzes the aziridination of electron-donating aryl azides and a wide variety of substituted aliphatic alkenes, including tetrasubstituted ones, in a "C(2) + N(1)" addition reaction. Finally, the catalyst can be recovered and reused up to three additional times without significant reduction in yield.

A dimeric macrocyclic tetra-N-heterocyclic carbene (NHC) silver complex was synthesized and shown to successfully extend transmetallation of polydentate NHCs beyond bidentate NHCs. The silver complex was utilized in the preparation of a variety of monomeric tetra-NHC complexes ranging from early first row to late third row transition metals in moderate to high yield for a total of nine examples of transmetallation. Among these complexes are rare examples of silver transmetallation with first row transition metals: chromium, iron, and cobalt. Additionally, the first examples of tetracarbenes on chromium and gold are reported. All compounds were characterized by single crystal X-ray diffraction, ESI-MS, and spectroscopic techniques.

18-Atom-ringed macrocyclic tetra-imidazolium ligands have been synthesized by a two-step procedure and are the smallest free tetra-imidazoliums to date. The structures of the tetra-imidazoliums were characterized by multinuclear NMR and high-resolution ESI/MS to distinguish them from the potential di-imidazolium species. These tetra-imidazolium ligands form monomeric tetra-carbene complexes of platinum through in situ deprotonation.

An iron(IV) tetrazene complex has been synthesized that is an important addition to a previously proposed catalytic aziridination cycle. It provides two key insights about the aziridination: an iron(IV) imide is formed and this imide can bind an additional ligand in the cis position.

Macrocyclic tetraimidazolium diborate ligand precursors with two different ring sizes have been synthesized by ring-forming reactions between diimidazoles and haloboranes. Deprotonation of the macrocyclic tetraimidazoliums with n-butyllithium followed by the addition of divalent metal salts of palladium or nickel leads to macrocyclic tetracarbene complexes with an 18-atom macrocycle, but not the 16-atom variant. These neutral palladium and nickel complexes are the first examples of macrocyclic tetracarbene diborate complexes, and unlike their cationic counterparts, they are highly soluble in nonpolar solvents. All macrocyclic tetraimidazoliums and their corresponding metal complexes were characterized by single-crystal X-ray diffraction and spectroscopic techniques.