Augmentation of Alkaline Earth Reactivity: An FLP Analogy

催化作用，加速化学转化，是实现传统（化石）和替代（例如生物质和二氧化碳）化学原料转化的环境友好和经济过程的关键。催化剂的作用是减少反应进行所需的能量，因此将在世界能源的未来中发挥关键作用。许多最有用的可溶性和固体催化剂都含有贵金属，如铑、钯、铂和钌。这些金属价格昂贵，而且供应有限。因此，有必要开发非贵金属催化剂作为替代品。为了响应这些要求，过去十年出现了s-和p-嵌段化合物作为廉价和生态良性的催化试剂。申请人之前的研究在第二组试剂的开发方面处于领先地位，特别是基于镁和钙（分别是地球上最丰富的八种和四种元素）的试剂，用于各种催化转化。虽然这包括一些最实际需要的转化，但目前可用的第2族试剂的用途受到其绝对反应性的限制。研究这些反应的详细机制方法使得这些以前未被重视的元素的化学反应性出现了更广泛的模型。这种理解是基于大多数底物分子与高电正性的2族中心结合所固有的极化模型。这些物质在底物分子上引起的电荷分离可以看作是与另一个新兴领域——“受挫”路易斯对化学密切相关的反应性的结果。在后一种情况下，各种各样的小分子可以通过高能空分子轨道和低能填充原子轨道的合作相互作用被激活。本提案希望将这一假设外推，将FLP概念应用于设计具有无与伦比反应性的新2族物种。这样，新试剂将使催化系统能够将第2组化学的环境和财政效益与增强且易于操纵的FLP反应性结合起来。

Catalysis, the acceleration of chemical transformation, is the key to realising environmentally friendly and economical processes for the conversion of both conventional (fossil) and alternative (e.g. biomass and carbon dioxide) chemical feedstocks. Catalysts act by reducing the energy required for a reaction to proceed and will, thus, occupy a key role in the world's energy future. Many of the most useful soluble and solid catalysts incorporate precious metals such as rhodium, palladium, platinum and ruthenium. These metals are expensive and their supply is limited. There is, therefore, a need for the development of non-precious-metal catalysts as replacements.In response to these requirements, the last decade has seen emergence of s- and p-block compounds as inexpensive and ecologically benign catalytic reagents. The applicant's previous research has led the way in the development of group 2 reagents, particularly those based on magnesium and calcium (the eight and four most earth-abundant elements respectively) for a wide variety of catalytic transformations. Although this has included some of the most practically desirable transformations, the usefulness of currently available group 2 reagents is limited by their absolute reactivity. A detailed mechanistic approach to the study of these reactions has allowed the emergence of more generalised models for the chemical reactivity of these previously under-appreciated elements. This understanding is based on a polarisation model intrinsic to the bonding of most substrate molecules to a highly electropositive group 2 centre. The charge separation induced across a substrate molecule by these species may be viewed as resulting from reactivity closely related to another emerging field, 'frustrated' Lewis pair chemistry. In this latter case, a wide variety of small molecules may be activated through a cooperative interaction of a high energy vacant molecular orbital and a low energy filled atomic orbital. This proposal wishes to extrapolate this hydpothesis to apply the FLP concept to design new group 2 species of unparalleled reactivity. In so doing the new reagents will enable catalytic systems that combine the environmental and fiscal benefits of group 2 chemistry with the enhanced and readily manipulated FLP reactivity.