A Combined Experimental and Computational Study of Bond Activation Reactions in Ruthenium N-Heterocyclic Carbene Complexes

钌N-杂环卡宾配合物中键活化反应的实验与计算联合研究

• 批准号: EP/F029292/1
• 负责人: Mike Whittlesey
• 金额: $ 35.02万
• 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: 2008
• 资助国家: 英国
• 起止时间: 2008 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=EP%2FF029292%2F1
• 关键词: Combined; Experimental; Computational; Study; Bond

A major application of transition metal (TM) complexes is in homogeneous catalysis. This provides low energy routes to the synthesis of both bulk chemicals (relatively simple molecules for use as solvents or feedstocks for more complicated products ) or fine chemicals (e.g. pharmaceuticals). To be successful, a TM catalyst must be stable, efficient and selective. This is usually achieved through the correct choice of ligand - a molecule that binds to the metal centre to control the reactive site. Traditionally phosphines have been the ligand of choice in TM catalysis, although in the last 15 years, a new class of ligand, the N-heterocyclic carbenes (NHCs), has been developed and in some cases these have met with spectacular success.One drawback with NHCs, however, is they are not themselves inert species, but will also undergo their own reaction chemistry. This has clear implications for catalyst performance, as it means the nature of the reactive site at the metal will change and possibly degrade with time. It is vital that this NHC-based reactivity is first understood and then controlled if new generations of catalysts featuring NHC as ligands are to be designed. This proposal builds on preliminary experimental observations in the Whittlesey group at Bath that have identified a number of unusual NHC-based reactions. In order to understand these processes it is imperative to deduce the mechanism(s) by which they occur. TM reaction mechanisms often take place through a number of individual steps which involve very short-lived reaction intermediates and transition states. Such species are difficult to study experimentally, but can be tackled using computational modelling. An effective approach is therefore to combine experimental observations (in the Whittlesey group) with complementary computational studies (performed by Macgregor's group at Heriot-Watt University) to provide extra insight into reactivity. In this proposal we will use experimental and computational methods to study a range of novel NHC-based reactions. Our aim is to rationalize the mechanisms of these processes and so to be able to define the conditions under which they occur. As these conditions are likely to pertain with many TM centres, we expect to provide very general information about the stability of TM-NHC species. Ultimately we seek to control NHC-based reactivity so that new catalysts can be designed where these detrimental processes can be avoided.Although detrimental for catalysis, NHC-based reactivity can also be viewed in a more positive light. NHCs often react through the cleavage of chemical bonds that are usually considered 'inert', or at least highly unreactive. In the present case a C-N bond cleavage reaction has been observed and by studying this and related (C-H, N-H and Ru-C) bond cleavage processes we also aim to provide fundamental information on how to break such bonds. This insight may then be used to activate such chemically unreactive bonds in other (non-NHC) systems.

过渡金属（TM）配合物的一个主要应用是在均相催化中。这提供了合成散装化学品（用作溶剂或更复杂产品的原料的相对简单的分子）或精细化学品（例如药物）的低能量路线。为了成功，TM催化剂必须稳定、高效和选择性。这通常是通过正确选择配体来实现的-配体是一种与金属中心结合以控制反应位点的分子。传统上膦配体一直是TM催化的首选配体，尽管在过去的15年里，一类新的配体，N-杂环卡宾（NHC），已经被开发出来，在某些情况下，这些已经取得了惊人的成功。这对催化剂性能有明显的影响，因为这意味着金属上反应位点的性质将随着时间的推移而改变并可能降解。如果要设计以NHC为配体的新一代催化剂，那么首先了解并控制这种基于NHC的反应性至关重要。这一提议建立在巴斯的Whittlesey小组的初步实验观察基础上，该小组已经确定了一些不寻常的基于NHC的反应。为了理解这些过程，必须推导出它们发生的机制。TM反应机理通常通过许多单独的步骤发生，这些步骤涉及非常短的反应中间体和过渡态。这些物种很难通过实验进行研究，但可以通过计算机建模来解决。因此，一种有效的方法是将联合收割机的实验观察（在Whittlesey小组中）与补充计算研究（由赫瑞瓦特大学的麦格雷戈小组进行）相结合，以提供对反应性的额外见解。在本提案中，我们将使用实验和计算方法来研究一系列基于NHC的新型反应。我们的目标是使这些过程的机制合理化，从而能够确定它们发生的条件。由于这些条件可能与许多TM中心有关，我们希望提供有关TM-NHC物质稳定性的非常一般的信息。最终，我们寻求控制NHC基反应性，以便设计新的催化剂，避免这些有害过程。尽管NHC基反应性对催化有害，但也可以从更积极的角度看待。NHC通常通过通常被认为是“惰性”或至少是高度不反应的化学键的断裂来反应。在这种情况下，C-N键裂解反应已被观察到，并通过研究这个和相关的（C-H，N-H和Ru-C）键裂解过程，我们还旨在提供有关如何打破这种键的基本信息。然后，这种见解可以用于激活其他（非NHC）系统中的化学不反应键。

项目成果

Three-coordinate nickel(I) complexes stabilised by six-, seven- and eight-membered ring n-heterocyclic carbenes: synthesis, EPR/DFT studies and catalytic activity.

• DOI: 10.1002/chem.201202950
• 发表时间: 2013-02
• 期刊: Chemistry
• 作者: M. Page;W. Lu;Rebecca C. Poulten;Emma Carter;Andrés G. Algarra;B. Kariuki;S. Macgregor;M. Mahon;K. Cavell;D. Murphy;M. Whittlesey

Ring-Expanded N-Heterocyclic Carbene Complexes of Ruthenium

• DOI: 10.1021/om901044u
• 发表时间: 2010-02-22
• 期刊: ORGANOMETALLICS
• 影响因子: 2.8
• 作者: Armstrong, Robert;Ecott, Christopher;Whittlesey, Michael K.
• 通讯作者: Whittlesey, Michael K.