Synthesis and Molecular Design of Novel Modified-Heteropolyanions Containing Multicenter Active Sites

本研究取得了以下几个新成果：1。在1,4,9 -三钒(V)取代Keggin多氧钨酸盐[1,4,9 - pw_9v_3o_ <40>]^<6->的V_3表面（b位）上合成了Cp^*Rh^<2+>配合物（Cp^* = C_5Me_5）。产物中还含有[Cp^*Rh(DMSO)_3]^<2+>。分离得到了三ti ^<IV>和二ti ^<IV>取代Keggin多氧钨酸盐，并测定了它们的x射线晶体结构。在水溶液中进行了超离心分子量（MW）测量。两种Ti^<IV>-取代物均为二聚体，分别为两种α-Keggin [1,2,3 - pw_9ti_3o_ <40>]^<9->单元和两种新型α-Keggin [1,2 - pw_ <10>Ti_2O_<40>]^<7->单元的Ti- o -Ti酸酐形式。溶液分子量测定表明，前者在pH7.0水溶液中为二聚体，后者在ph7.8水溶液中为单体。合成了三金属取代的Dawson多氧钨酸盐[P_2W_<15>M_3O_<62>]^<9-> (M = Nb^V, V^V)与有机金属基团（(cod)Pt^<2+>和Cp^*Rh^<2+>）之间的负载型多氧钨酸盐，并阐明了多氧阴离子载体（Nb vs. V）和有机金属基团（(cod)Pt^<2+> vs. Cp^*Rh^<2+>）的影响。采用GC/MS分析了几种钒(V)取代的Keggin和Dawson多金属氧酸盐在30% H_2O_2水溶液中催化甲苯和硝基苯的氧化产物。对通过离子机制和自由基机制促进反应的多金属氧酸盐进行了分类。

Several novel results in this research were obtained :1. The Cp^*Rh^<2+> complex (Cp^* = C_5Me_5) supported on the V_3 surface (B-site) of 1, 4, 9-tri-vanadium(V)-substituted Keggin polyoxotungstate [1, 4, 9-PW_9V_3O_<40>]^<6-> was synthesized. The product also contained [Cp^*Rh(DMSO)_3]^<2+> as counterion.2.Tri-Ti^<IV>-and di-Ti^<IV>-substituted Keggin polyoxotungstate were isolated as potassium salts and their X-ray crystal structures determined. Ultracentrifugation molecular weight (MW) measurements were also performed in aqueous solution. The two Ti^<IV>-substituted compounds in the solid state were dimeric, Ti-O-Ti anhydride forms of two α-Keggin [1, 2, 3-PW_9Ti_3O_<40>]^<9-> units and of two novel α-Keggin [1, 2-PW_<10>Ti_2O_<40>]^<7-> units, respectively. Solution MW measurements showed that the former was a dimer in pH7.0 aqueous solution, whereas the latter was a monomer in pH 7.8 aqueous solution.3. The supported-polyoxotungstates formed between tri-metal-substituted Dawson polyoxotungstate [P_2W_<15>M_3O_<62>]^<9-> (M = Nb^V, V^V) and organometallic groups ((cod)Pt^<2+> and Cp^*Rh^<2+>) were synthesized, and the effects polyoxoanion-support (Nb vs. V) and organometallic species ((cod)Pt^<2+> vs. Cp^*Rh^<2+>) were elucidated.4. Oxidation products of toluene and nitrobenzene with 30% aqueous H_2O_2 catalyzed by several vanadium(V)-substituted Keggin and Dawson polyoxometalates were carefully analyzed by GC/MS measurements. Polyoxometalates which promote the reaction via an ionic mechanism and via a radical mechanism were classified.