Two Novel Polyoxometalate-Based Metal–Organic Complexes with Chiral Waugh-Type [MnMo9O32]6–Anions as High-Efficiency Catalytic Oxidative Desulfurization Catalysts

Two novel polyoxometalates (POMs)-based metal–organic complexes (MOCs) [Co3(4-H2dpye)(MnMo9O32)(H2O)10]·H2O (1) and [Co3(4-H2dpyb)(MnMo9O32)(H2O)12]·4H2O (2) have been designed and synthesized under hydrothermal conditions by introducing the chiral Waugh-type [MnMo9O32]6–into the transition metal cobalt–bis(pyrimidine)–bis(amide) systems. Single crystal X-ray diffraction shows that 1and 2are racemic complexes containing both left-handed and right-handed [MnMo9O32]6–polyoxometalate anions. In complex 1, the chiral [MnMo9O32]6–anions are coordinated to the [Co3(4-H2dpye)(H2O)10]n6n+metal–organic units to build a 2D layered structure containing the left- and right-handed [MnMo9O32]6–-based chains. While complex 2consists of a 1D metal–organic chain [Co3(4-H2dpyb)(H2O)12]n6n+and the isolated [MnMo9O32]6–anions. Complexes 1and 2can be expanded into the racemic 3D supramolecular frameworks through extensive hydrogen bonding interactions. Complexes 1and 2can be used as high-efficiency heterogeneous catalysts for the oxidation of methyl phenyl sulfide (MBT). The effects of reaction solvent, temperature, amount of catalysts, and oxidant on the catalytic performance of MBT oxidation reaction were investigated. In addition, complexes 1and 2can be used as versatile and efficient catalysts for thioether oxidation. Importantly, Waugh-type [MnMo9O32]6–-based MOCs as oxidative desulfurization catalysts have rarely been reported.