Oxidation of Carbon Monoxide Cocatalyzed by Palladium(0) and the H5PV2Mo10O40 Polyoxometalate Probed by Electron Paramagnetic Resonance and Aerobic Catalysi

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• 作者：Hila Goldberg ; Ilia Kaminker ; Daniella Goldfarb ; Ronny Neumann
• 刊名：Inorganic Chemistry
• 出版年：2009
• 出版时间：August 17, 2009
• 年：2009
• 卷：48
• 期：16
• 页码：7947-7952
• 全文大小：847K
• 年卷期：v.48,no.16(August 17, 2009)
• ISSN：1520-510X

文摘

The H₅PV₂Mo₁₀O₄₀ polyoxometalate and Pd/Al₂O₃ were used as co-catalysts under anaerobic conditions for the activation and oxidation of CO to CO₂ by an electron transfer-oxygen transfer mechanism. Upon anaerobic reduction of H₅PV₂Mo₁₀O₄₀ with CO in the presence of Pd(0) two paramagnetic species were observed and characterized by continuous wave electron paramagnetic resonance (CW-EPR) and hyperfine sublevel correlation (HYSCORE) spectroscopic measurements. Major species I (65−70%) is assigned to a species resembling a vanadyl cation that is supported on the polyoxometalate and showed a bonding interaction with ¹³CO. Minor species II (30−35%) is attributed to a reduced species where the vanadium(IV) atom is incorporated in the polyoxometalate framework but slightly distanced from the phosphate core. Under aerobic conditions, CO/O₂, a nucleophilic oxidant was formed as elucidated by oxidation of thianthrene oxide as a probe substrate. Oxidation reactions performed on terminal alkenes such as 1-octene yielded a complicated mixture of products that was, however, clearly a result of alkene epoxidation followed by subsequent reactions of the intermediate epoxide. The significant competing reaction was a hydrocarbonylation reaction that yielded a 1:1 mixture of linear/branched carboxylic acids.