The Oxidation Of Styrene Catalyzed By Poms-based Compounds And Coordination Polymers

POMs-based compounds play an important role in the field of inorganic chemistry.Compounds can exhibit different structures,such as 1D chain,2D network,3D structures and so on,by the functionalization of the polyoxometalates moiety and the connection of organic ligands.There are many kinds of synthetic techniques,such as hydrothermal,normal temperature and so on.Moreover,PH,temperature,time,the kind and ratio of materials have a great impact on the synthesis of the compound.Because of its complex composition,complicated and diverse structure,polyoxometalates have been applied in many fields and attract many scientists’attention.Coordination polymers are formed by the coordination of metal ions and organic ligands.It has the characteristics of both organic ligands and inorganic metal ions.Therefore,it has a wide application in many fields,such as catalysis,porous material and so on.The synthesis and properties of coordination polymers are research hotspots in recent years.In this paper,we focused on the coordination among organic ligands,metal and clusters.We determined and analyzed the crystal structure by using X-ray single crystal diffraction technique.On the former basis,a series of characterization methods were also carried out.The catalytic performance of compounds for the oxidation of styrene was explored.In order to further explore the role of polyoxometalates in the oxidation of styrene,we explored the catalytic effect of coordination polymers with 2-methyl-5-mercapto-1,3,4-thiadiazole（hmthd）as organic ligand.1.Using hydrothermal synthesis,five metal-oxide clusters（compounds 1-5）have been successfully synthesized.Among them,compound 1 was first synthesized.It has the Dawson-type metal-oxide cluster,while compound 2 has a Keggin-type metal-oxide cluster with one-dimension chain structure.The clusters’structure of compounds3-5 were all Keggin-type.For compounds 1 and 2,they were used as catalysts in the oxidation reaction of styrene to explore the relationship between the catalytic effect and many parameters.[Cu（2,2′-bpy）（nicn）][Cu₂（2,2′-bpy）₃（nicn）][P₂W₁₈O₆₂]（1）[{Cu₃^I（phen）}₃Cl₂]{[Cu^II（phen）₂][Cu₂^II（phen）]}₂(α-PW₁₁O₃₉)（2）[Cu（4,4′-bipy H）₃（4,4′-bipy）][HPW₁₂O₄₀]₂·12H₂O（3）[Cu₄（2,2′-bpy）₄（H₂O）₂（PO₄）₂]（H₃O）[PMo₁₂O₄₀]（4）[Si W₁₂O₄₀][Cu（2,2′-bpy）₂]₂·10H₂O（5）2.Four cooperation compounds（compounds 6-9）were used to explored the catalytic performance of the oxidation of styrene.Among them,two neutral Hmthd ligands interact with one{Cu Cl}moiety to form a mononuclear coordination compound（compound 6）.Compounds 7-9 exhibit two-dimensional layered structure.We explored the optimal reaction conditions and further speculated the reaction mechanism by using free radical scavengers.Experiment results indicate that compound 7 performed extremely enhanced catalytic activity for the oxidation of styrene and had a low activation energy.In the process of the experiment of compound8 and 9,we found that the addition of an appropriate amount of acid can promote the protonation of ligands and improve their conversions.[Cu（Hmthd）₂Cl]_n（1）[Cu₃（mthd）₂Br]_n（2）[Ag（mthd）]_n（3）[Ag₂（mthd）I]_n（4）...