Electronic Structure and Multicatalytic Features of Redox-Active Bis(arylimino)acenaphthene (BIAN)-Derived Ruthenium Complexes
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- 作者：Arijit Singha Hazari ; Ritwika Ray ; Md Asmaul Hoque ; Goutam Kumar Lahiri
- 刊名：Inorganic Chemistry
- 出版年：2016
- 出版时间：August 15, 2016
- 年：2016
- 卷：55
- 期：16
- 页码：8160-8173
- 全文大小：864K
- 年卷期：0
- ISSN：1520-510X
文摘
The article examines the newly designed and structurally characterized redox-active BIAN-derived [Ru(trpy)(R-BIAN)Cl]ClO4 ([1a]ClO4–[1c]ClO4), [Ru(trpy)(R-BIAN)(H2O)](ClO4)2 ([3a](ClO4)2–[3c](ClO4)2), and BIAO-derived [Ru(trpy)(BIAO)Cl]ClO4 ([2a]ClO4) (trpy = 2,2′:6′,2′′-terpyridine, R-BIAN = bis(arylimino)acenaphthene (R = H (1a+, 3a2+), 4-OMe (1b+, 3b2+), 4-NO2 (1c+, 3c2+), BIAO = [N-(phenyl)imino]acenapthenone). The experimental (X-ray, 1H NMR, spectroelectrochemistry, EPR) and DFT/TD-DFT calculations of 1an–1cn or 2an collectively establish {RuII–BIAN0} or {RuII–BIAO0} configuration in the native state, metal-based oxidation to {RuIII–BIAN0} or {RuIII–BIAO0}, and successive electron uptake processes by the α-diimine fragment, followed by trpy and naphthalene π-system of BIAN or BIAO, respectively. The impact of the electron-withdrawing NO2 function in the BIAN moiety in 1c+ has been reflected in the five nearby reduction steps within the accessible potential limit of −2 V versus SCE, leading to a fully reduced BIAN4– state in [1c]4–. The aqua derivatives ({RuII–OH2}, 3a2+–3c2+) undergo simultaneous 2e–/2H+ transfer to the corresponding {RuIV═O} state and the catalytic current associated with the RuIV/RuV response probably implies its involvement in the electrocatalytic water oxidation. The aqua derivatives (3a2+–3c2+) are efficient and selective precatalysts in transforming a wide variety of alkenes to corresponding epoxides in the presence of PhI(OAc)2 as an oxidant in CH2Cl2 at 298 K as well as oxidation of primary, secondary, and heterocyclic alcohols with a large substrate scope with H2O2 as the stoichiometric oxidant in CH3CN at 343 K. The involvement of the {RuIV═O} intermediate as the active catalyst in both the oxidation processes has been ascertained via a sequence of experimental evidence.