Bond Activation - the Remarkable Emerging Chemistry of Bis(carboranes)

这项建议试图理解并建立在申请人实验室最近发现的三个引人注目的反应的基础上。在第一个反应中，芳香族C-C键在室温下在金属碳硼烷(主要是硼、碳和金属的簇合物)中裂解，金属碳硼烷来自双碳硼烷(两个连接的碳/硼原子簇)。这种反应是引人注目的，因为芳烃中的C-C键非常强，通常被认为很难打破。在第二个反应中，也是在室温下，一个不同的双碳硼烷分子在还原和随后与金属碎片反应时，似乎从其一半失去了两个碳顶点，作为一个完整的C2单位。这种方式的脱碳在杂硼烷化学中是前所未有的。最后的反应(也是在室温下)明确地确认了相关的一碳碳烷的脱碳反应；这也是史无前例的。综上所述，第一和第二反应涉及双(碳硼烷)，第三反应始于具有非常强的吸电子取代基的碳硼烷。显然，这些史无前例的反应在某种程度上与这些碳硼烷的非标准性质有关。不知怎么的，双碳硼烷和高度修饰的碳硼烷正在促进传统上非常高能量的过程中的键断裂反应。这两种碳硼烷的化学成分目前都严重不发达。该提案试图通过彻底调查双(碳硼烷)和碳硼烷与电子缩合取代基的反应来解决这种情况，特别是重点是脱碳或还原，然后是金属化或碳化。我们完全期待这项研究将揭示除了最近发现的那些之外的其他意想不到的和新的反应。通过一个全面的合成化学计划，我们将试图识别和理解我们所发现的显着反应的起源。一旦我们理解了它们，我们就能更好地确定它们的共性以及如何使用它们。

This proposal seeks to understand and build on three remarkable reactions recently discovered in the applicant's laboratory. In the first reaction an aromatic C-C bond is cleaved at room temperature in a metallacarborane (a cluster compound of [mainly] boron, carbon and metal) derived from a bis(carborane) (two linked carbon/boron clusters). The reaction is remarkable because C-C bonds in arenes are extremely strong and generally considered difficult to break. In the second reaction, again at room temperature, a different bis(carborane) molecule appears to lose two carbon vertices from one of its halves as an intact C2 unit on reduction and subsequent reaction with a metal fragment. Such decarbonation in this way is unprecedented in heteroborane chemistry. The final reaction (again room temperature) confirms unambiguoulsy decarbonation from a related monocarborane; again this is without precedent.In summary then, the first and second reactions involve bis(carboranes) and the third starts with a carborane with very strongly electron-withdrawing substituents. It seems apparent that these unprecedented reactions are in some way linked to the non-standard nature of these carboranes. Somehow the bis(carborane) and the highly modified carborane are promoting bond cleavage reactions that are traditionally very high energy processes. The chemistries of both these types of carborane are currently severely under-developed. The proposal seeks to address this situation by a thorough investigation of the reactions of bis(carboranes) and of carboranes with e-withdrawing substituents, focussing in particular on deboronation or reduction followed by metallation or capitation. We fully expect that this study will reveal other unexpected and novel reactions in addition to those recently found.Through a comprehensive synthetic chemistry programme we will seek to identify and understand the origins of the remarkable reactions we have discovered. Once we understand them we will be in a much better position to establish their generality and how they might be used.