Redox Noninnocence of the Bridge in Copper(II) Salophen and Bis(oxamato) Complexes.
Two square-planar copper(II) complexes of 1,2-bis(2-hydroxy-3,5-di-tert-butylbenzimino)-4,5-bis(dimethylamino)benzene (1) and N-[4,5-bis(dimethylamino)-2-(oxalylamino)benzene]oxamate (22-) were prepd. The crystal structures of the proligands H2L1 (3) and Et2H2L2 (4), as well as the corresponding complexes, are reported. The proligands each display a one-electron-oxidn. wave, which is assigned to oxidn. of the bis(dimethylamino)benzene moiety into a $π$ radical. Complexes 1 and 22- exhibit reversible one-electron-oxidn. waves in their cyclic voltammograms (E1/21 = 0.14 and E1/22 = 0.31 V for 1 and E1/21 = -0.47 V vs. Fc+/Fc for 22-). The first process corresponds to oxidn. of the bis(dimethylamino)benzene central ring into a $π$ radical, while the second process for 1 is ascribed to oxidn. of the $π$ radical into an $\alpha$-diimino quinone. The one-electron-oxidized species 1+ and 2- exhibit intense visible-near-IR absorptions, which are diagnostic of $π$ radicals. They display a triplet signal in their ESR spectra, which stem from magnetic coupling between the ligand-radical spin and the copper(II) spin. The zero-field-splitting parameters are larger for 2- than 1+ because of greater delocalization of the spin d. onto the coordinated amidato N atoms. D. functional theory calcns. support a $π$-radical nature of the one-electron-oxidized complexes, as well as S = 1 ground spin states. The electrogenerated 12+ comprises a closed-shell diimino quinone ligand coordinated to a copper(II) metal center. Both 1 and 2 catalyze the aerobic oxidn. of benzyl alc., albeit with different yields. [on SciFinder(R)]
Références
- Titre
- Redox Noninnocence of the Bridge in Copper(II) Salophen and Bis(oxamato) Complexes.
- Type de publication
- Article de revue
- Année de publication
- 2015
- Auteurs
- de Bellefeuille, David, Orio Maylis, Barra Anne-Laure, Aukauloo Ally, Journaux Yves, Philouze Christian, Ottenwaelder Xavier, and Thomas Fabrice
- Revue
- Inorg. Chem.
- Volume
- 54
- Pagination
- 9013–9026
- ISSN
- 0020-1669
- Mots-clés
- benzaldehyde prepn benzyl alc oxidn copper hydroxytertbutylbenzimino dimethylaminobenzene dimethylaminooxalylaminobenzeneoxamate complex catalyst crystal structure copper hydroxytertbutylbenzimino dimethylaminobenzene dimethylaminooxalyl aminobenzeneoxamate complex cyclic voltammetry copper hydroxytertbutylbenzimino dimethylaminobenzene dimethylaminooxalyl aminobenzeneoxamate complex EPR spectra copper hydroxytertbutylbenzimino dimethylaminobenzene dimethylaminooxalyl aminobenzeneoxamate complex mol structure optimization copper hydroxytertbutylbenzimino dimethylaminobenzene dimethylaminooxalyl aminobenzeneoxamate complex oxidn copper hydroxytertbutylbenzimino dimethylaminobenzene dimethylaminooxalylaminobenzeneoxamate complex catalyst prepn copper hydroxytertbutylbenzimino dimethylaminobenzene dimethylaminooxalyl aminobenzeneoxamate complex
Soumis le 12 avril 2018