Organo-Ruthenium substituted Polyoxoanions and Their Homogeneous Oxidation Catalysis Properties

我们提出用顺磁性的、具有氧化还原活性的过渡金属中心取代新的、离散的多钨氧酸盐分子。我们的重点是那些结合的过渡金属可以通过两个或更多的末端配体立体接近的物种。这将允许定向和结合有机底物分子，如果可能的话，以区域和立体选择的方式。我们对固有手性聚阴离子的合成特别感兴趣，这是一个迄今为止还没有系统研究的领域。该合成策略包括过渡金属前驱体与适当的空腔聚阴离子配体的反应。在这个项目中，我们将重点研究含有杂原子的孤对多金属氧酸盐（如AsIII， SbIII）。对于多重氧化还原活性过渡金属中心，我们将研究8族元素Fe3+， Ru2+和Os2+。迄今为止，只有少数具有上述特征的含Fe3+杂多阴离子得到了结构表征，其催化活性的初步结果是非常有希望的。有趣的是，迄今为止还没有报道含有Ru2+或Os2+异多阴离子的孤对结构。新化合物的结构将通过单晶x射线衍射、多核磁共振、电子和振动光谱进行表征。新型多金属氧酸盐的催化活性将被测试，主要目的是设计新的、高效的氧化系统，采用环保的O2或H2O2作为主要氧化剂。这些多金属簇是有吸引力的物种，因为它们具有显著的特性，包括热降解和氧化降解的高稳定性，通过反离子复分解（从水到有机介质和全氟烃）可调节的溶解度，纳米尺寸，克级合成和光催化活性。我们的方法将侧重于(i)使用一些基准氧化转化进行催化剂筛选；（ii）通过评估催化剂负载、稳定性和过程范围来优化反应；（iii）机制研究；（iv）在绿色/替代溶剂（例如水、氟化液体）中最大限度地减少对环境的影响；(v)使用替代激活技术，包括微波辐射（MW）和光照射（hv）。拟议中的合作将汇集在多金属氧酸盐工程和合成、固态和溶液形成、均相和非均相催化、机理研究和对环境问题的关注等方面具有互补专业知识的实验室。

We propose to synthesize novel and discrete polyoxotungstate molecules substituted by paramagnetic, redox-active transition metal centers. Our emphasis is on species where the incorporated transition metals are sterically accessible by having two or more terminal ligands. This will allow for orienting and binding of the organic substrate molecule, if possible in a regio- and stereoselective fashion. We are particularly interested in the synthesis of intrinsically chiral polyanions, an area which has not been worked on systematically to date. The synthetic strategy encompasses reaction of a transition metal precursor with the appropriate lacunary polyanion ligand. In this project we will focus on polyoxometalates with lone-pair containing hetero atoms (e.g. AsIII, SbIII). Regarding the multiple, redox-active transition metal centers we will study the group 8 elements Fe3+, Ru2+ and Os2+. To date only a handful of Fe3+ containing heteropolyanions with the above characteristics have been structurally characterized and the preliminary results of catalytic activity are highly promising. Interestingly, no structure of a lone pair containing heteropolyanion of Ru2+ or Os2+ has been reported to date. The structures of the novel compounds will be characterized by single-crystal X-ray diffraction, multinuclear NMR, electronic and vibrational spectroscopy. The catalytic activity of the novel polyoxometalates will be tested with the principal aim to design new, efficient oxidation systems employing environmentally friendly O2 or H2O2 as primary oxidants. These multi-metal clusters are attractive species because of their noticeable properties including high stability with respect to thermal and oxidative degradation, tunable solubility via counterion metathesis (from water to organic media and also perfluorohydrocarbons), nano-sized dimensions, gram-scale synthesis and photocatalytic activity. Our approach will focus on (i) catalyst screening using some benchmark oxidative transformations, (ii) reaction optimisation by evaluating catalyst loading, stability, and scope of the process (iii) mechanism investigation (iv) minimisation of the environmental impact in green/alternative solvents (e.g. water, fluorinated liquids), (v) use of alternative activation techniques including microwave irradiation (MW) and photoirradiation (hv). The proposed collaboration will bring together laboratories with complementary expertise on polyoxometalate engineering and synthesis, solid state and solution speciation, homogeneous and heterogeneous catalysis, mechanistic investigation and attention to environmental issues.