Studies of the reactivity of iridium(II) coordination complexes with two-electron chemical oxidants

High valent transition metal complexes are often found to be reactive with other substances. For example, ruthenium(VI) bis-oxo porphyrin species epoxidize a large number of substrates in the presence of two-electron chemical oxidants, oxygen atom donors in particular. This type of reactivity should be investigated further with other platinum group metals, which are known to facilitate a multitude of transformations of organic molecules, in part because they bind well with organic supporting ligands and substrates. The work described here explores the reactivity of a number of novel and known iridium(III) complexes with 2-electron chemical oxidants, in attempts to synthesize and study the oxidative reactivity of iridium(V) complexes. Chapter 1 gives a broad overview of the reactivity of high valent iridium complexes. It also discusses aspects of our methodology in designing the systems of interest, including iridium(III) complex design, as well as precedent for using two-electron chemical oxidants. Chapter 1 concludes by briefly introducing an electrochemical oxidation project that served as an interlude between the two major iridium(III) oxidation projects. Chapter 2 describes the synthesis of new Cp*Ir(L-L)X complexes (L-L = bidentate ligand) and discusses the reactivity between the iridium complexes and two-electron chemical oxidants. In these systems, chemical oxidants generally reacted with ligands rather than the metal center of our iridium(III) complexes. For example, [Cp*IrCl2] 2 and Cp*Ir(ppy)Me reacted with the iodine(III) reagent PhI(OAc) 2 to acetoxylate a methyl group on the Cp* ligand(s). Chapter 3 focuses on attempts to synthesize iridium(V) oxo porphyrin species by reacting coordinatively saturated and unsaturated iridium(III) porphyrin complexes with oxygen atom donors. Oxygen atom donors reacted with the axial ligands of the metalloporphyrin complexes, or they coordinated to the metal center. This is contrary to the reactivity of many other transition metal porphyrins (Fe, Mn, Ni, Ru, etc.), which react with oxygen donors to form oxo metalloporphyrin complexes. Finally, Chapter 4 describes our attempts to use a cobalt-phosphate anode to oxidize water-soluble organic substrates, including amines and ethylene glycol. The anode was not effective for oxidizing the organic substrates that we tested, but can be seen as quite robust in the presence of organic "contaminants."...