The focus of this project in the Inorganic, Bioinorganic and Organometallic Chemistry Program is the chemistry of high and unusual oxidation states of transition metals, such as copper(III), cobalt(IV) and cobalt(V). The project is expected to result in the discovery of useful and powerful new oxidizing agents, as well as providing biomimetic models of certain metalloenzymes which have recently been found to contain metals in high oxidation states, such as galactose oxidase, which contains copper(III). Square planar cobalt(III) complexes and their anionic precursors will be studied and employed as precursors to highly oxidized organometallic species. These complexes utilize oxidation-resistant polyanionic chelating (PAC) ligands. Oxygen atom transfers catalyzed by these species will be pursued especially by a search for terminal cobalt(IV)-oxo complexes. The recently discovered copper(III) complexes which oxidize alcohols will be studied as biomimetic models of galactose oxidase and related enzymes and will also be used in a general exploration of the role of copper(III) complexes in oxidation processes. Evidence will be sought for intermediates in the oxidation of phosphine to phosphine oxide by molecular oxygen catalyzed by osmium(VI)/(IV) systems. Ruthenium complexes of PAC ligands will be investigated as possible catalysts for alkene oxidations by molecular oxygen. "Thermodynamic ladders" will be developed to interrelate the formal reduction potentials and isomerization equilibria of diastereomeric complexes of the first thermodynamically stable nonplanar amides, and these amides will be compared to their planar analogues. The electrochemistry in liquid sulfur dioxide of new complexes of the highly protected PAC ligands will be explored in a search for solution stable one-electron oxidants with formal reduction potentials greater than 2.5 V vs. NHE. Attempts will be made also to extend the electrochemical measurements to other solvents offering a wide anodic range.
