多元多金属含氧簇合物在催化化学中的应用

多金属含氧簇合物在催化化学中的重要性与日俱增，在原子经济反应和环境友好催化方面有着诱人的实用前景。这类物种的催化活性、理化性质、分子结构和固态体相结构以及制备方法均能在分子水平上给出详细信息，因而被视为混合金属氧化物催化剂的分子设计材料。本文拟对能够直观反映出这种信息的多元多金属含氧簇合物催化的研究作一评述。     

线性低价铂系金属簇合物的研究

长链线性配合物具有特有的结构、成键和性质，在分子器件和特殊性能低维材料等方面展示出潜在的应用前景。在低价状态下，铂系金属可自聚合形成一类含有多个金属原子的线性金属链式簇合物。本文就有关线性低价铂系金属簇合物的研究进展作一简述。     

M_nP_m~+原子簇结构的ab initio从头算(M=Cr,Mn,n=1～3,m=2～12)

应用ahinitio计算程序，我们对飞行时间质谱产生的谱图进行了理论分析。稳定的MnnPm+和CrnPm+的结构基本上是多面体，仅有少数结构为环状和平面的。在计算中，我们尚未发现有链状的簇合物，这与风簇绝大多数是多面体是相一致的。因此，单枚金属簇合物的形成机制很大可能是金属进入磷形成的笼簇中。一般地说，除了磷的个别笼状团簇外，金属和磷相互成键是普遍存在的；在二核、多核金属磷簇合物中，金属间相互作用不常见，绝大多数是通过桥磷相连的。     

锌硅钼钨多元取代多金属含氧簇合物的合成、表征及其催化异丙醇气相反应的活性

利用pH值的调变, 以H₄SiMo_12－nW_nO₄₀•(20～25)H₂O (n＝2, 4, 6, 8, 10)和Zn(NO₃)₂饱和溶液为原料制得一系列锌硅钼钨多元取代多金属含氧簇合物, 通过IR, XRD, XPS等方法对合成的催化剂的结构和性质进行了表征, 并利用吡啶吸附红外及氨程序升温脱附分别测定样品表面的酸种类和酸强度. 考察了催化剂对异丙醇气相反应的活性, 同时详细研究了异丙醇气相反应产物分布与催化剂组成之间的关系.     

立方烷型四核IB族金属-钨簇合物电子结构的从头算研究

采用从头算方法和自然成键轨道分析对双核鹤硫簇合物[W2S4（SH2）2]2-和立方烷型四核异金属鸽硫簇合物W2MM’（SH2）2（PH3）Cu2,Ag2,CuAg）的电子结构进行研究。研究结果表明，钨簇合物与相簇合物具有相似的电子结构特征，金属原子间均存在不同程度的直接成键和通过桥原子或端原子的明显的多中心d-pπ键，还讨论了这种多中心镇对于簇加成反应及簇合物稳定性的影响。     

K4H2[SiW5Mo6Mn(H2O)O39]·22H2O的晶体结构

合成了一个锰硅钼钨四元取代含氧簇合物,用单晶X射线衍射方法测定了结构,该晶体属于四方晶系,空间群P4/mnc,a=14.119(3),c=12.496(4),V=2490.9(12)3,Mr=2862.70,z=2,Dc=3.817g*cm-3,μ=15.922mm-1,R=0.0462,wR=0.1232.锰硅钼钨阴离子中,中心SiO4四面体在C4轴的两个位置上是无序的.     

无机-有机多金属砷钒氧簇合物的合成及研究进展

多金属砷钒氧簇合物由于具有结构多样性、优良的物理特性以及广泛的应用前景而引起人们的关注。该类簇合物的合成战略是将有机配体和过渡金属配合物连接到砷钒氧骨架上以获得各种新奇结构。按此策略人们合成出一系列新奇的无机有机砷钒氧簇合物。本文综述了多金属砷钒氧簇合物的合成方法、结构性质等方面的研究进展,并对其今后研究前景进行了展望。     

过渡金属簇合物合成化学

本文以与催化作用紧密相关的金属羰基簇合物的合成和与化学仿生相关的铁硫和钼铁硫簇合物的合成为例,评述了过渡金属簇合物合成化学的发展概况,给出了金属-金属间键合的两条通则(低氧化态金属间容易成键和同一族元素中重金属具有较大的成键倾向)和三类簇合物的主要合成路线。     

「VS_4-Cu_n」簇合物的固相合成、结构规律和成簇机理的研究

以(NH_4)_3VS_4为起始原料与CuCl在低温团相不同反应条件下,得到了不同簇骼的[VS_4-CU_n]的簇合物,并总结了CuCl/(NH_4)_3VS_4不同摩尔比、不同反应温度和时间对簇合物生成的影响和[VS_4-Cu_n]簇合物的结构规律.同时探索了V-Cu-S簇合物固相合成的成簇机理.     

中心氧三核过渡金属羰基簇合物的穆斯堡尔谱研究

中心氧三核过渡金属羰基簇合物的穆斯堡尔谱研究王友桐（中国科学院福建物质结构研究所，福州，３５０００２）关键词：三核簇合物，穆斯堡尔谱学引言由于三重桥氧三核铁、铬羰基簇合物具有特殊的结构特征、磁性、催化性能和电子特性，已引起了许多学者的兴趣￣［１－３］...     

Chiral Dawson‐Type Hybrid Polyoxometalate Catalyzes Enantioselective Diels–Alder Reactions

Can achiral organocatalysts linked to chiral polyanionic metal oxide clusters provide good selectivity in enantioselective C?C bond formations? The answer to this question is investigated by developing a new active hybrid polyoxometalate‐based catalyst for asymmetric Diels–Alder reaction. Chirality transfer from the chiral anionic polyoxometalate to the covalently linked achiral imidazolidinone allows Diels–Alder cycloaddition products to be obtained with good yields and high enantioselectivities when using cyclopentadiene and acrylaldehydes as partners.     

Polyoxometalates covalently bonded with terpyridine ligands

A terpyridine ligand is covalently linked to a hexamolybdate cluster through the Mo-N imido bond, paving the way for the preparation of hybrids containing covalently bonded transition metal complexes and polyoxometalate clusters.     

Designed Assembly of Heterometallic Cluster Organic Frameworks Based on Anderson‐Type Polyoxometalate Clusters

A new approach to prepare heterometallic cluster organic frameworks has been developed. The method was employed to link Anderson‐type polyoxometalate (POM) clusters and transition‐metal clusters by using a designed rigid tris(alkoxo) ligand containing a pyridyl group to form a three‐fold interpenetrated anionic diamondoid structure and a 2D anionic layer, respectively. This technique facilitates the integration of the unique inherent properties of Anderson‐type POM clusters and cuprous iodide clusters into one cluster organic framework.     

Archimedean Synthesis and Magic Numbers: "Sizing" Giant Molybdenum-Oxide-Based Molecular Spheres of the Keplerate Type

Pythagorean harmony can be found in the spherical polyoxometalate clusters described here (see illustration for an example of a structure), since there are interesting relationships between the so-called magic numbers (12, 32, 42, 72, 132) relevant for spherical viruses and the number of the building blocks in the cluster. The size of these Keplerate clusters can be tailored by varying the type of connections between the pentagons by means of different spacers.     

A low dielectric constant polyimide/polyoxometalate composite

A silane‐modified mono‐lacunary Keggin‐type polyoxometalate (POM), (Bu₄N)₄[SiW₁₁O₃₉{(CH₂?CH? Si)₂O}] (SiW₁₁? CH?CH₂), was obtained by reaction of vinyltrimethoxysilane with K₈(SiW₁₁O₃₉) in acidic MeCN/H₂O mixed solutions. Then, the modified polyoxometalate was physically blended with the pyromellitic dianhydride (PMDA)‐4,4′‐oxydianiline (ODA) poly(amic acid) and the blends were thermally imidized to form polyimide/ polyoxometalate composites. The X‐ray diffraction (XRD) analysis indicates that the polyoxometalate clusters cannot form crystalline structures in the composite, suggesting that the blending leads to improved compatibility between the polymer matrix and the modified polyoxometalate. The EDS (W‐mapping) studies on the composite films reveal that the polyoxometalate clusters are well dispersed in the polyimide matrix. The physical incorporation of modified POM into polyimide remarkably reduced the dielectric constant of the latter from 3.29 to 2.05 when 20 wt% of SiW₁₁? CH?CH₂ was used. Besides, the addition of the modified POM into polyimide increased the storage modulus of polyimide without severely affecting its thermal properties. Copyright © 2009 John Wiley & Sons, Ltd.     

Twining Poly(polyoxometalate) Chains into Nanoropes

Organic polymers and inorganic clusters belong to two different disciplines and have completely different properties and structures. When a cluster is attached to the backbone of a polymer as a pendant, the resultant hybrid polymers (polyclusters) exhibit unique behaviours totally different from those of conventional polymers owing to the nanoscale size of the cluster and its particular interactions. Herein, the aggregation of a poly(polyoxometalate)—a polynorbornene backbone with inorganic polyoxometalate cluster pendants—upon addition of a non-solvent to its dilute solution is reported. A three-dimensional network of tangled and snake-like nanothreads was observed. Direct visualisation of individual nanoscale clusters enabled identification of single chains within the nanothreads. These observations suggest that during the process of aggregation, the hybrid polymer forms curved or extended chains as a consequence of an armouring effect in which the collapsed cluster pendants wrap around the backbone. The collapse occurs because they become less soluble in the solvent/non-solvent mixture. The extended chains then become entwined and form nanoropes consisting of multiple chains wound around each other. This study provides a deeper understanding of the nature of polyclusters and should also prove useful for their future development and application.     

Layer-by-layer inkjet printing of fabricating reduced graphene-polyoxometalate composite film for chemical sensors

Graphene oxide (GO) nanosheets and polyoxometalate such as H(3)PW(12)O(40) (PTA) are prepared into a multilayer film via a layer-by-layer inkjet printing method. The GO/PTA composite thin film shows linear, uniform and regular layer-by-layer growth. Under UV-irradiation, a photoreduction reaction takes place in the film which converts GO to reduced GO (rGO) due to the photoreduction activity of polyoxometalate clusters. According to the cyclic voltammograms measurement, the rGO/PTA composite film displays good electrocatalytic activity for the oxidation of dopamine (DA). The oxidation peak current (I(pa)) increases gradually with increasing the dopamine concentration, which may be used in electrochemical biosensors.     

Towards polyoxometalate-integrated nanosystems

Polyoxometalates represent a diverse range of molecular clusters with an almost unmatched range of physical properties and the ability to form structures that can bridge several length scales. The new building block principles that have been discovered are beginning to allow the design of complex clusters with desired properties and structures; several structural types and novel physical properties are examined herein. The overall message that is presented throughout is the possibility that polyoxometalate clusters could be excellent candidates to be exploited in the development of functional nanosystems or nanodevices. The concepts that underpin the development of nanoscale devices are discussed briefly, as are the considerable challenges that must be overcome to realise polyoxometalate-based functional nanosystems.