Construction And Catalysis Of Pd(Ⅱ)/POMs Polymer:Pd(Ⅱ)/POMs Efficiently Catalyzes The Suzuki-Miyaura Coupling Reaction

Polyoxometalates（POMs）are a type of polyoxygen clusters.Due to their strong electronegativity,some oxygen atoms are easily coordinated with transition metal atom to develop new inorganic hybrid materials.（NH₄）₆Mo₇O₂₄·4H₂O can be converted into polyoxometalates of different configurations at high temperature and is widely used.Because Pd element possessed excellent catalytic activity in organic synthesis,the development of high-efficiency Pd/POMs hybrid catalyst has always been the focus of study.In this paper,the classic polyoxometalate（NH₄）₆Mo₇O₂₄·4H₂O is selected as the basic building unit,and Pd（OAC）₂ is selected as the Pd source.Through the mixed solvothermal method,five monoatomic Pd/POMs are synthesized sequentially catalyst.If changing the ratio of the solvent and the reaction temperature are used five kinds of Pd/POMs polymers can be obtained in sequence,and the loading of Pd increases in sequence.In view of the dual considerations of Pd/POMs catalyst structure and Pd loading,we selected catalysts 4 and 3 to catalyze a series of Suzlki-Miyaura reactions,and obtained good yields.Since its discovery in 1979,the Suzlki-Miyaura reaction has been used in drug synthesis,chemistry and chemical engineering,and development of new materials due to its advantages such as mild reaction conditions,few side reactions,wide substrate applicability,high yield and convenient.In this paper,five new Pd/POMs heterogeneous catalysts were prepared by the mixed solvothermal method,which have the advantages of high catalytic activity,recyclability,high selectivity,and easy recovery.At the same time,the development of five kinds of Pd and POMs catalysts makes it possible to develop and apply more Pd/POMs catalysts.Specific study content of this paper is as follows:（I）Using Pd（OAC）₂ and（NH₄）₆Mo₇O₂₄·4H₂O as the initial reactants,changing the content of Pd（OAC）₂ and（NH₄）₆Mo₇O₂₄·4H₂O,the ratio of the reaction solvent CH₃CN and H₂O and the reaction temperature,the cascade synthesis of five kinds of Pd/POMs catalyst.A series of Suzuki-Miyaura catalyzed by the novel structure 3 also obtained outstanding yields.The chemical formulas of the five catalysts are as follows:1[Pd（H₂O）₄]_0.5[Mo₇O₂₄]·5H₃O·3H₂O;2[Pd（H₂O）₄]₂[Mo₇O₂₄]·2H₃O·H₂O;2’[Pd（H₂O）₄]₂[Mo₇O₂₄]·2H₃O·H₂O;3[Pd（H₂O）₄][Mo₄O_13.5]·H₃O;4[Pd（H₂O）₄][Pd（H₂O）₃Mo₄O₁₄]·2H₂O;（II）Phenylboronic acid（C₆H₇BO₂）and bromobenzene（C₆H₅Br）were used as a model reaction.4 was used to catalyze the model reaction and the optimal reaction conditions were screened out.Afterwards,five kinds of catalysts were used to catalyze the model reaction and good yields were obtained.A series of Suzuki-Miyaura reactions catalyzed by 4 and all got good yields.Furthermore,the universality use of 4 in organic coupling synthesis were also confirmed by the reactions below,（a）5-bromofuran-2-carbaldehyde,a derivative of furfural compound（b）3-bromo-7-（diethylam-ino）-2H-chromium-2-Ketone,a kind of fluorescent probe intermediate（c）the reaction between methyl（E）-3-（1-benzyl-6-bromo-1H-1H-indol-3-yl）acrylate a kind of indole drug intermediate and p-tolyl boronic acid.These results indicate that the Pd/POMs catalyst prepared by us is highly efficient and can be widely used.