Two U(VI)-Containing Silicotungstates with Sandwich Structures: Lewis Acid-Base Synergistic Catalyzed Synthesis of
1Jiangxi Province Key Laboratory of Synthetic Chemistry, Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China University of Technology, Nanchang 330013, China.
Abstract:
Two new U(VI)-containing silicotungstates with similar sandwiched polyanions but different space structures, two-dimensional Na10.5H3.5(H2O)36[Na(UO2)(α-SiW9O34)]2·2.5H2O (1) and three-dimensional Na14(H2O)36[Na(UO2)(α-SiW9O34)]2·4H2O (2), have been synthesized by the reactions of UO2(OAc)2 and Na10[α-SiW9O34]·18H2O in aqueous solution at different pH values. Structure analyses demonstrated that different reaction conditions may provide different self-assembly conditions and result in the different coordination environments of Na(I)-H2O clusters with different disorders, which are the keys to the differences between 1 and 2. Compound 2 was demonstrated to show excellent catalytic activity for the synthesis of 3H-benzo[b][1,4]diazepines and pyrazoles via the intermolecular cyclization reactions, and the yields of the desired products reached 99%. This work illustrates the catalytic properties for U(VI)-containing POMs.
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