|Ph.D Student||Golubkov Galina|
|Subject||Catalysis of Atom - and Group - Transfer by Metal Corroles|
|Department||Department of Chemistry||Supervisor||Professor Zeev Gross|
The recently introduced methodologies for the synthesis of 5,10,15-triarylcorroles allow for extensive investigations of corroles in the many applications where porphyrins are constantly utilized, while introducing features that are unique to corroles. We have developed two approaches for obtaining (nitrido)manganese(V) complexes of the trianionic 5,10,15-tris(pentafluorophenyl)corrolato ligand (tpfc): irradiation of azide-coordinated manganese(III) and oxidation of ammonia-coordinated manganese(III) corroles by various reagents. In a conceptually similar way, the reaction of ammonium hydroxide and bleach with chromium(III) corrole allowed for the isolation of the novel (nitrido)chromium(VI) complex. A very different route to the same complexes relies on nitrogen-atom-transfer from (nitrido)manganese(V) salen. Investigation of the above process between metal complexes of different macrocycles revealed that stabilization of the [Mn(N)]2+ moiety is in the order of corrole > porphyrin >> salen. The first ever kinetic investigation of this fundamental reaction revealed a large solvent effect ( MeCN > MeOH > THF), which was rationalized via elucidation of the activation parameters (enthalpy and entropy). Oxidation of the already high-valent (nitrido)manganese(V) corroles led to novel manganese(VI) complexes.
We further found that the pyrrole-brominated corrole also forms a stable nitrido complex and, more surprisingly, that its analogous (oxo)manganese(V) corrole can be isolated. The latter complex was found to be more thermally stable than the non-brominated analog, but much more reactive towards organic substrates. All complexes were characterized by various spectroscopic methods and electrochemistry, as well as with regard to their reactivity as reagents for transferring a nitrogen or oxygen atom to other metal complexes or organic substrates. These studies shine new light on the unique properties of the corrole metal complexes and demonstrate their advantages in catalytic processes.