Molecular s-block Assemblies for Redox-active Bond Activation and Catalysis: Repurposing the s-block as 3d-elements

通过催化调节反应的能量需求在解决大量商品、制药和精细化工过程的动力学可行性方面发挥着至关重要的作用。目前的催化剂利用率水平使CA。每年一千九百亿美元这一数字预计将在2025年升至2270亿美元。同样清楚的是，一个真正循环和可持续经济的未来繁荣将需要对我们的催化科学基本方法进行投资。因此，创新的催化模式，以及更广泛的化学合成模式，将继续成为科技进步的主要驱动力，并成为新应用的种子，以实现COVID-19疫情后绿色复苏的目标。特别地，均相催化继续由铂族金属（PGM，例如Rh、Ir、Pd、Pt）主导。然而，这些元素的持续和日益增加的实施受到高成本、易受影响的供应及其相对较高的毒性的威胁。这些因素刺激了当代的重点识别的替代催化载体产生的系统来自地球上丰富的轻过渡金属和主族（s-和p-块）的元素。然而，要实现这一目标，需要全球作出巨大努力，设计创新手段，有效利用这一广泛的、高度不同的化学品。特别是镁和钙的地质可用性确保了这些元素比PGM便宜几个数量级，同时它们的吸引力因其通常良好的环境影响和生物相容性而突出。虽然这些系统现在包含了广泛的多键杂官能化和交叉偶联催化剂，无一例外的个别键活化过程发生在定义的两个电子步骤，并通过维持极其稳定的Ae（II）氧化态。尽管随着对Ae（II）阳离子的半径和极化率的调节而产生显著的可变性，但后一特征排除了氧化还原活性和可调HOMO-LUMO能量的任何可能性，所述能量由催化性PGM的nd价轨道的可用多样性产生。Soc.2021，143，17851），包含低氧化态Mg-Mg键合单元和两个钠阳离子的杂多酸组装体可通过还原常规分子Mg（II）双苯胺容易地获得。{Mg 2Na 2}组装体的电子结构和化学性质不仅取决于形式上Mg（I）中心的存在，而且还取决于Mg-Mg键与钠阳离子的协同相互作用。在这个建议中，我们提出了一个联合合成和计算研究，利用这个一般的设计原则，并访问一个家庭的正式低氧化态组1 /组2异双金属。所得到的化合物将具有窄的和可操纵的前沿轨道能量，这将允许前所未有地进入显示可逆氧化还原行为的s-块系统。这些化合物将有助于探索它们对小分子如H2，CO，CO2和N2的反应性，而它们潜在的氧化还原活性将使催化歧管的构建成为可能，这些歧管与过渡金属的nd轨道构型相比，与孤立的第1和第2族中心相比，具有更高的共性。

The moderation of a reaction's energy demands through catalysis plays a vital role in addressing the kinetic viability of a vast array of commodity, pharmaceutical and fine chemical processes. The current level of catalyst utilisation enables ca. $190 billion p.a. of domestic revenue for the UK, a value that it is estimated will rise to $227 bn by 2025. It is also clear that the future prosperity of a truly circular and sustainable economy will require investment in our fundamental approaches to catalytic science. Innovative modes of catalysis and, more generally, chemical synthesis, therefore, will continue to be primary drivers for the advancement of science and technology and a seed corn for new applications to meet the objectives for a green recovery in the aftermath of the COVID-19 pandemic. Homogeneous catalysis, in particular, continues to be dominated by platinum group metals (PGMs, e.g. Rh, Ir, Pd, Pt). The continued and growing implementation of these elements, however, is threatened by a combination of high cost, vulnerable supply and their relatively high toxicity. These factors have stimulated a contemporary focus on the identification of alternative catalytic vectors resulting from systems derived from the more earth abundant lighter transition metals and main group (s- and p-blocks) of elements. The fulfilment of this objective, however, requires a massive global effort to devise innovative means to productively harness this broad palette of highly disparate chemistry. The geological availability of, in particular, magnesium and calcium ensures that these elements are orders of magnitude less expensive than PGMs, while their appeal is underscored by their generally benign environmental impact and biocompatibility. Although these systems now encompass a wide range of multiple bond heterofunctionalization and cross coupling catalyses, without exception the individual bond activation processes occur in defined two electron steps and through the maintenance of the extremely stable Ae(II) oxidation state. Although significant variability arises with adjustments to the radii and polarizability of the Ae(II) cations, this latter feature precludes any possibility of the redox activity and tuneable HOMO-LUMO energies that arise from the available manifold of nd valence orbitals of catalytic PGMs.This proposal builds on the applicants' recent discovery (J. Am. Chem. Soc. 2021, 143, 17851) that a heterobimetallic assembly comprising a low oxidation state Mg-Mg bonded unit and two sodium cations is readily accessible by reduction of a conventional molecular Mg(II) bis-anilide. The electronic structure and chemistry of the {Mg2Na2} assembly is dependent not only on the presence of the formally Mg(I) centres but also on the cooperative interaction of the Mg-Mg bond with the sodium cations. In this proposal, we present a joint synthetic and computational study to exploit this general design principle and access a family of formally low oxidation state group 1 / group 2 heterobimetallics. The resultant compounds will possess narrow and manipulable frontier orbital energies that will allow unprecedented access to s-block systems that display reversible redox behaviour. These compounds will facilitate an exploration of their reactivity toward small molecules such as H2, CO, CO2 and N2, while their potential redox activity will enable the construction of catalytic manifolds, which display a higher degree of commonality with those derived from the nd orbital configurations of transition metals than those of isolated group 1 and 2 centres.