Stabilization of High Oxidation States on Transition Metal Complexes
Date
2009-05
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Publisher
University of Delaware
Abstract
Redox active ligands, i.e. ligands that can be reduced or oxidized, are of considerable interest due to the fact that they potentially have the ability to stabilize unusual metal species. Previous work done by Wieghardt as well as by our lab has shown that two prime examples of these types of ligands are dithiolene and α-diimine complexes. This work has shown that in some instances these ligands themselves are oxidized, while other times the metal oxidation state is altered. With this in mind, we set out to explore the use of 1,1’-diaminoferrocene (dafc), a redox active complex, as a ligand with divalent metal cations. The reasoning is that the ligand’s metal center, with its increased electron density (as compared to main block elements such as carbon, nitrogen, oxygen, and their respective groups), may be able to aid in oxidation-reduction reactions and achieve otherwise rare metal oxidation states. Our work focused primarily on cobalt, which contains a large number of electrons in its d orbitals (nine in the zero-valent state). Our attempts also spilled over into metal with fewer available d electrons, such as titanium, vanadium, chromium and manganese. Synthetic routes have been explored for these compounds, yet all failed to produce the desired ligand-metal complex. Theories for the failure of current synthetic routes, as well as possible alternatives, are presented. While these compounds were not able to be synthesized in the duration of this project, the proposed compounds present an interesting study and their potential in ligand based oxidation-reduction chemistry can not be effectively ruled out.