The H5PV2Mo10O40 polyoxometalate and Pd/AI2O3 were used as co-catalysts under anaerobic conditions for the activation and oxidation of CO to CO 2 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 hydro-carbonylation reaction that yielded a ∼1:1 mixture of linear/branched carboxylic acids.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry