Photocatalytic Hydroxylation of Benzene by Dioxygen to Phenol with a Cyano-Bridged Complex Containing FeII and RuII Incorporated in Mesoporous Silica–Alumina
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- 作者：Yusuke Aratani ; Kohei Oyama ; Tomoyoshi Suenobu ; Yusuke Yamada ; Shunichi Fukuzumi
- 刊名：Inorganic Chemistry
- 出版年：2016
- 出版时间：June 20, 2016
- 年：2016
- 卷：55
- 期：12
- 页码：5780-5786
- 全文大小：457K
- 年卷期：0
- ISSN：1520-510X
文摘
Photocatalytic hydroxylation of benzene to phenol was achieved by using O2 as an oxidant as well as an oxygen source with a cyano-bridged polynuclear metal complex containing FeII and RuII incorporated in mesoporous silica–alumina ([Fe(H2O)3]2[Ru(CN)6]@sAl-MCM-41). An apparent turnover number (TON) of phenol production per the monomer unit of [Fe(H2O)3]2[Ru(CN)6] was 41 for 59 h. The cyano-bridged polynuclear metal complex, [Fe(H2O)3]2[Ru(CN)6], exhibited catalytic activity for thermal hydroxylation of benzene by H2O2 in acetonitrile (MeCN), where the apparent TON of phenol production reached 393 for 60 h. The apparent TON increased to 2500 for 114 h by incorporating [Fe(H2O)3]2[Ru(CN)6] in sAl-MCM-41. Additionally, [Fe(H2O)3]2[Ru(CN)6] acts as a water oxidation catalyst by using [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) and Na2S2O8 as a photosensitizer and a sacrificial electron acceptor as evidenced by 18O-isotope labeling experiments. Photoirradiation of an O2-saturated MeCN solution containing [Fe(H2O)3]2[Ru(CN)6]@sAl-MCM-41 and scandium ion provided H2O2 formation, where photoexcited [Ru(CN)6]4– moiety reduces O2 as indicated by laser flash photolysis measurements. Thus, hydroxylation of benzene to phenol using molecular oxygen photocatalyzed by [Fe(H2O)3]2[Ru(CN)6] occurred via a two-step route; (1) molecular oxygen was photocatalytically reduced to peroxide by using water as an electron donor, and then (2) peroxide thus formed is used as an oxidant for hydroxylation of benzene.