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

用于氧化还原活性键活化和催化的分子 s 块组装：将 s 块重新用作 3d 元素

• 批准号: EP/X01181X/1
• 负责人: Michael Hill
• 金额: $ 145.64万
• 依托单位: University of Bath
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FX01181X%2F1
• 关键词: Molecular; block; Assemblies; Redox; active

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.

通过催化调节反应的能量需求在解决大量商品、制药和精细化学过程的动力学可行性方面起着至关重要的作用。目前的催化剂利用水平为英国每年带来约1900亿美元的国内收入，预计到2025年将增加到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我们对催化科学的基本方法进行投资。因此，创新的催化模式，以及更广泛的化学合成模式，将继续成为推动科技进步的主要动力，并为新应用提供种子，以实现2019冠状病毒病大流行后的绿色复苏目标。特别是均相催化，继续由铂族金属（pgm，如Rh， Ir, Pd, Pt）主导。然而，这些元素的持续和不断增加的使用受到高成本、易受伤害的供应和相对高毒性的综合威胁。这些因素激发了当代人们对鉴定由更丰富的轻质过渡金属和主要元素群（s-和p-块）衍生的体系所产生的替代催化载体的关注。然而，这一目标的实现需要大规模的全球努力，以设计创新手段，有效地利用这一广泛的高度不同的化学调色板。特别是镁和钙的地质可用性确保了这些元素比铂基金属便宜几个数量级，而它们的吸引力则因其一般无害的环境影响和生物相容性而得到强调。虽然这些系统现在包含了广泛的多键异功能化和交叉偶联催化剂，但无一例外，单个键激活过程发生在定义的两个电子步骤中，并通过维持极其稳定的Ae（II）氧化态。尽管随着Ae（II）阳离子的半径和极化率的调整，会产生显著的变化，但后一种特征排除了氧化还原活性和可调节的HOMO-LUMO能量的任何可能性，这些能量来自于催化pgm的有效和价轨道的流形。这个建议建立在申请人最近的发现之上（J. Am.）。化学。Soc. 2021, 143, 17851)表明，一个由低氧化态Mg-Mg键合单元和两个钠离子组成的杂双金属组装体很容易通过还原传统分子Mg（II）双苯胺得到。{Mg2Na2}组装体的电子结构和化学性质不仅取决于形式上的Mg(I)中心的存在，而且取决于Mg-Mg键与钠离子的合作相互作用。在本提案中，我们提出了一项联合合成和计算研究，以利用这一一般设计原则，并获得了一类正式低氧化态的1 / 2族杂金属化合物。合成的化合物将具有窄且可操纵的边界轨道能量，这将允许前所未有地进入显示可逆氧化还原行为的s-嵌段体系。这些化合物将有助于探索它们对H2、CO、CO2和N2等小分子的反应性，而它们潜在的氧化还原活性将有助于构建催化歧管，这些歧管与来自过渡金属和轨道构型的化合物相比，显示出更高程度的共性。

项目成果

Cesium Reduction of a Lithium Diamidochloroberyllate

二氨基氯铍酸锂的铯还原

• DOI: 10.1021/acs.organomet.3c00519
• 发表时间: 2024
• 期刊: Organometallics
• 影响因子: 2.8
• 作者: Pearce K