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Isolating an Inner-Sphere Adduct of [Ru IV (═O)(terpy)(bpy)] 2+ and [Ce IV (OH)(NO 3 ) 5 ] 2- with the Oxo Bonded to the Ce IV Center.
- Source :
-
Journal of the American Chemical Society [J Am Chem Soc] 2024 Jun 06. Date of Electronic Publication: 2024 Jun 06. - Publication Year :
- 2024
- Publisher :
- Ahead of Print
-
Abstract
- Water oxidation is a key to achieving sustainable energy cycles, for which higher-valent metal-oxo species often play a key role to accelerate the rate-limiting O-O bond formation. The present study undertook efforts to clarify one of the steps postulated for the water oxidation (WO) catalyzed by [Ru <superscript>II</superscript> (terpy)(bpy)(OH <subscript>2</subscript> )] <superscript>2+</superscript> (terpy = 2,2':6',6″-terpyridine, bpy = 2,2'-bipyridine). This study focuses on inner-sphere electron transfer for the Ce <superscript>IV</superscript> -driven oxidation of the Ru <superscript>IV</superscript> ═O species into the Ru <superscript>V</superscript> ═O species. The approach to this step became possible by inventing a feasible method to isolate an air-stable Ru <superscript>IV</superscript> ═O powder sample in this work. Importantly, by mixing the thus-obtained Ru <superscript>IV</superscript> ═O sample with CAN (cerium ammonium nitrate), the inner-sphere adduct [Ru <superscript>IV</superscript> (═O)(terpy)(bpy)][Ce <superscript>IV</superscript> (NO <subscript>3</subscript> ) <subscript>5</subscript> (OH)] was successfully isolated. The IR spectrum of the isolated adduct exhibits a strong band at 774 cm <superscript>-1</superscript> attributable to the Ru <superscript>IV</superscript> ═O-Ce <superscript>IV</superscript> stretching vibration, proving covalent bonding of the oxo to the Ce <superscript>IV</superscript> center. Furthermore, the absorption spectrum of this greenish black powder shows a broad absorption band at 600 nm, suggesting a charge transfer transition from the π* orbital of Ru <superscript>IV</superscript> ═O to the 4f orbital of Ce <superscript>IV</superscript> , as supported by TD-DFT calculations. The addition of one equivalent of CAN to the Ru <superscript>IV</superscript> ═O solution induces the spectral change due to formation of the 1:1 adduct identical to the isolated adduct. Our study provides a clue to the formation of an inner-sphere adduct having a Ru <superscript>IV</superscript> ═O-Ce <superscript>IV</superscript> core in the Ce <superscript>IV</superscript> -driven WO catalysis.
Details
- Language :
- English
- ISSN :
- 1520-5126
- Database :
- MEDLINE
- Journal :
- Journal of the American Chemical Society
- Publication Type :
- Academic Journal
- Accession number :
- 38843404
- Full Text :
- https://doi.org/10.1021/jacs.4c05389