The synthesis of inorganic paddlewheel and iron-sulfur complexes in reduced oxidation states

by Scott, Thomas A.

THE SYNTHESIS OF INORGANIC PADDLEWHEEL AND IRON-SULFUR COMPLEXES IN REDUCED OXIDATION STATES By Thomas A. Scott The traditional divisions of chemistry have continually become less distinct as our chemical knowledge increases. Inorganic metal complexes have become quite useful in catalysis, as models of protein active sites, and in medical treatments. One of the challenges faced by synthetic inorganic chemists has been the development of chemical syntheses designed to isolate metal complexes in reduced states. This dissertation is divided into roughly two research areas: paddlewheel complexes and iron-sulfur clusters. The first section discusses the syntheses of hetero-bimetallic paddlewheel complexes, where opposite ends of a paddlewheel complex are occupied by different metal centers (M–M?). There have been only a few examples of this type of complex in the literature. This is mainly due to the inherent difficulties in synthesizing such a complex, including metal scrambling and regio isomerization. In order to gain a better understanding of M–M? interactions, a synthetic method to overcome these synthetic difficulties has been developed. The second section discusses the synthesis of iron-sulfur clusters as models for active sites in proteins. The field of synthetic iron-sulfur protein analogues has developed steadily since the early 1970’s and identification of protein bound iron-sulfur clusters occurred during the same era. As crystallographic techniques became routine, proteins were identified that contained these clusters in reduced states or in sitedifferentiated coordination environments. However, the synthetic analogues have proven difficult to synthesize, isolate, and characterize for their increased oxidative sensitivity when removed from the protein environment. The synthetic methodology discussed in this dissertation has overcome some of the above challenges. A series of hetero-bimetallic paddlewheel complexes, in which Pt and a first row transition metal have formed the desired paddlewheel complexes in high yields, are discussed in the first section of this dissertation. The isolation and characterization of the first all-ferrous 4Fe-4S analogue along with the syntheses of some 1:3 site differentiated clusters are discussed in the second section of this dissertation. The Synthesis of Inorganic Paddlewheel and Iron-Sulfur Complexes in Reduced Oxidation States A Dissertation Submitted to the Faculty of Miami University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Chemistry and Biochemistry By Thomas A. Scott Miami University Oxford, Ohio 2006 Dissertation Director: Hongcai Zhou