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Reversible osmium(VI) nitrido to osmium(II) ammine interconversion in complexes containing polypyrazolyl ligands
E S El-Samanody1, K D Demadis, T J Meyer
1Department of Chemistry, Venable and Kenan Laboratories, CB 3290, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3290, USA.
Inorganic Chemistry
|July 10, 2001
Summary
This study shows a reversible chemical reaction between ammonia (NH3) and azide (N3-) using osmium complexes. This interconversion is key for understanding electron and proton transfer in osmium chemistry.
Area of Science:
- Inorganic Chemistry
- Organometallic Chemistry
- Electrochemistry
Background:
- Osmium complexes with tris(1-pyrazolyl)methane (tpm) or hydrotris(1-pyrazolyl)borate anion (Tp) ligands are investigated.
- The interconversion between ammonia (NH3) and azide (N3-) is a significant chemical transformation.
Purpose of the Study:
- To describe the reversible 4e-/3H+ interconversion between NH3 and N3- in osmium complexes.
- To characterize the intermediates and products of this redox process.
Main Methods:
- Electrochemical and chemical reduction of osmium nitrido complexes.
- Isolation and structural characterization of osmium ammine complexes.
- Electrochemical reoxidation studies to elucidate reaction mechanisms.
Main Results:
- Osmium nitrido complexes ([Os(VI)(tpm)(Cl)2(N)]+ and Os(VI)(Tp)(Cl)2(N)) were reduced to Os(II)-ammine complexes ([Os(III)(tpm)(Cl)2(NH3)](PF6) and Os(III)(Tp)(Cl)2(NH3)).
- The Os(III)-ammine complexes were successfully reoxidized to the nitrido complexes.
- The reoxidation proceeds via stepwise mechanisms involving electron and proton loss and sequential Os(III-->IV) and Os(IV-->VI) oxidations.
Conclusions:
- The 4e-/3H+ interconversion between NH3 and N3- is demonstrated to be reversible in the coordination spheres of specific osmium complexes.
- The study provides insights into the stepwise redox processes governing osmium nitrido-ammine interconversions.