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/F029039/1
• 负责人: Stuart Macgregor
• 金额: $ 33.74万
• 依托单位: Heriot-Watt University
• 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%2FF029039%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）配合物的主要应用是均相催化。这为合成大宗化学品（相对简单的分子，用作更复杂产品的溶剂或原料）或精细化学品（例如药品）提供了低能量路线。为了获得成功，TM 催化剂必须稳定、高效且具有选择性。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，膦一直是 TM 催化中选择的配体，尽管在过去 15 年中，已经开发出一类新型配体，N-杂环卡宾 (NHC)，并且在某些情况下取得了巨大的成功。一个缺点然而，对于 NHC 来说，它们本身并不是惰性物质，但也会经历自己的化学反应。这对催化剂性能具有明显的影响，因为这意味着金属反应位点的性质将发生变化，并可能随着时间的推移而降解。如果要设计以 NHC 作为配体的新一代催化剂，首先了解并控制这种基于 NHC 的反应性至关重要。该提议建立在巴斯 Whittlesey 小组的初步实验观察的基础上，这些观察发现了一些不寻常的基于 NHC 的反应。为了理解这些过程，必须推断出它们发生的机制。 TM 反应机制通常通过许多单独的步骤进行，其中涉及非常短暂的反应中间体和过渡态。这些物种很难通过实验进行研究，但可以通过计算模型来解决。因此，一种有效的方法是将实验观察（在 Whittlesey 小组中）与补充计算研究（由赫瑞瓦特大学 Macgregor 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 的新颖反应。我们的目标是合理化这些过程的机制，从而能够定义它们发生的条件。由于这些条件可能与许多 TM 中心有关，因此我们希望提供有关 TM-NHC 物种稳定性的非常一般的信息。最终，我们寻求控制基于 NHC 的反应性，以便设计新的催化剂，避免这些有害过程。尽管对催化有害，但也可以从更积极的角度看待基于 NHC 的反应性。 NHC 通常通过化学键的断裂进行反应，这些化学键通常被认为是“惰性”的，或者至少是高度不反应的。在本例中，我们观察到了 C-N 键断裂反应，通过研究该反应以及相关的（C-H、N-H 和 Ru-C）键断裂过程，我们还旨在提供有关如何断裂此类键的基本信息。然后，这种见解可用于激活其他（非 NHC）系统中的此类化学惰性键。

项目成果

Computational Study of the C - and N -Bound Tautomers of [Ru(Cl)(H)(CO)-(PPh 3 ) 2 (I i PrMe 2 )] (I i PrMe 2 = 3-Isopropyl-4,5-dimethylimidazol-2-ylidene)

[Ru(Cl)(H)(CO)-(PPh 3 ) 2 (I i PrMe 2 )] (I i PrMe 2 = 3-异丙基-4,5-) C 和 N 结合互变异构体的计算研究

• DOI: http://dx.10.1002/ejic.200801228
• 发表时间: 2009
• 期刊: European Journal of Inorganic Chemistry
• 影响因子: 2.3
• 作者: Häller L

Smooth C(alkyl)-H bond activation in rhodium complexes comprising abnormal carbene ligands.

包含异常卡宾配体的铑配合物中的 C（烷基）-H 键顺利激活。

• DOI: http://dx.10.1039/c1dt11116g
• 发表时间: 2011
• 期刊: 2003)
• 作者: Krüger A

Experimental and computational investigation of C-N bond activation in ruthenium N-heterocyclic carbene complexes.

钌N-杂环卡宾配合物中C-N键活化的实验和计算研究。

• DOI: 10.1021/ja109702h
• 发表时间: 2010-12-03
• 期刊: Journal of the American Chemical Society
• 影响因子: 15
• 作者: L. J. L. Häller;M. Page;Stefan Erhardt;S. Macgregor;M. Mahon;M. Naser;Andrea Vélez;M. Whittlesey
• 通讯作者: M. Whittlesey

The influence of N-heterocyclic carbenes (NHC) on the reactivity of [Ru(NHC)(4)H](+) with H(2), N(2), CO and O(2).

N-杂环卡宾 (NHC) 对 [Ru(NHC)(4)H]( ) 与 H(2)、N(2)、CO 和 O(2) 反应性的影响。

• DOI: http://dx.10.1002/chem.200901736
• 发表时间: 2009
• 期刊: Chemistry (Weinheim an der Bergstrasse, Germany)
• 作者: Burling S

Formation of [Ru(NHC)4(eta(2)-O2)H]+: an unusual, high frequency hydride chemical shift and facile, reversible coordination of O2.

[Ru(NHC)4(eta(2)-O2)H] 的形成：不寻常的高频氢化物化学位移和容易的可逆 O2 配位。

• DOI: http://dx.10.1021/ja9039345
• 发表时间: 2009
• 期刊: Journal of the American Chemical Society
• 影响因子: 15
• 作者: Häller LJ