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

该提案旨在理解并建立在申请人实验室最近发现的三种显著反应的基础上。在第一个反应中，芳香族的C-C键在室温下被切割成金属碳硼烷（一种主要由硼、碳和金属组成的簇状化合物），它是由双碳硼烷（两个相连的碳/硼簇）衍生而来。这一反应非常引人注目，因为芳烃中的碳-碳键非常牢固，通常被认为难以断裂。在第二个反应中，同样是在室温下，另一个碳硼烷分子在还原和随后与金属碎片的反应中，作为完整的C2单元，似乎从它的一半中失去了两个碳顶点。这种脱碳方式在异硼烷化学中是前所未有的。最后的反应（同样是室温）明确地证实了相关的单碳硼烷的脱碳；这也是没有先例的。综上所述，第一和第二反应涉及碳硼烷，而第三反应以碳硼烷为起点，碳硼烷具有很强的吸电子取代基。很明显，这些前所未有的反应在某种程度上与这些碳硼烷的非标准性质有关。碳硼烷和高度修饰的碳硼烷促进了传统上高能的键裂解反应。这两种碳硼烷的化学性质目前严重不发达。该提案试图通过对双碳硼烷和碳硼烷与电子撤回取代基的反应进行彻底的研究来解决这一问题，特别关注在金属化或头化之后的波化或还原反应。我们完全期待这项研究将揭示除了最近发现的那些意想不到的和新颖的反应。通过一个综合的合成化学计划，我们将寻求确定和了解我们所发现的非凡反应的起源。一旦我们理解了它们，我们就能更好地确定它们的普遍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.