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Four Alkoxohexavanadate-Based Pd-Polyoxovanadates as Robust Heterogeneous Catalysts for Oxidation of Benzyl-Alkanes

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journal contribution
posted on 16.02.2015, 00:00 authored by Ji-Kun Li, Xian-Qiang Huang, Song Yang, Hong-Wei Ma, Ying-Nan Chi, Chang-Wen Hu
Four alkoxohexavanadate-based Pd-POVs [Pd­(dpa)­(acac)]2­[V6O13(OMe)6] (1), [Pd­(dpa)­(acac)]2­[V6O11­(OMe)8] (2), [Pd­(dpa)­(acac)]2­[V6O11­(OMe)8]­·H2O (3), and [Pd­(DMAP)2­(acac)]2­[V6O11­(OMe)8]­·H2O (4) (POV = polyoxovanadate; dpa = 2,2′-dipyridine amine; DMAP = 4-dimethylaminopyridine; acac = acetylacetone anion) have been synthesized and fully characterized by single crystal X-ray diffraction and powder X-ray diffraction analyses, Fourier transform infrared spectroscopy, element analyses, and X-ray photoelectron spectroscopy. In 14, Pd complexes and hexavanadate anions are assembled through electrostatic interactions. Interestingly, the [V6O11(OMe)8]2– cores in 2 and 3 are a pair of isomers that can be isolated by controlling crystallization temperature. Moreover, to the best of our knowledge, the {V6} core in 3 represents a new octamethoxyhexavanadates cluster. It is notable that compounds 14 exhibit excellent heterogeneous catalytic performance in the oxidation of benzyl-alkanes with t-butylhydroperoxide as oxidant. Among them, the catalytic activity of 1 (conv. and selec. up to 99%, respectively) outperforms others and can be reused without losing its activity.