Do we really understand the bonding in transition metal organometallic complexes?

过渡金属有机金属配合物在各种各样的应用中发挥着关键作用。它们从用于聚合物合成的兆吨级到用于制药工业的药物发现的毫克级。此外，最近的工作已经探索了有机金属在材料化学（例如有机发光二极管材料）和医疗保健中作为新型治疗剂的使用。有机金属配合物备受赞誉的优点之一是能够基于配体的空间和电子性质的系统变化来发展结构-活性关系。原则上，这些可以用于为新的或现有的应用提供具有有利性质的新金属配合物的设计。为了量化在金属配位范围内改变共配体的影响，已经设计了许多度量，也许最著名的是托尔曼在20世纪70年代。在这些研究中，选择一个给定的光谱参数（如羰基配体的拉伸频率）作为金属上这些电子变化的报告基团。例如，通过记录一系列化合物的红外光谱，人们认为可以评估共配体对金属上电子密度的影响。更现代的方法集中在多参数的方法来解决这个问题，然而，一个共同的主题是，从一个共配体的分析数据被用作报告。因此，根据定义，所有这些方法都是配体效应的间接测量，并且有许多例子表明，配体效应的性质可能因所使用的报告复合物而异。因此，在许多情况下，我们对金属-配体相互作用的理解是间接的。我们建议探索新的方法来直接量化有机金属化学中的配体效应，这些方法将不依赖于报告配合物的制备，而是直接涉及对感兴趣的金属或配体的测量。为了实现这一目标，我们将采用多种不同的光谱和分析方法的组合，这些方法在有机金属化学中很少使用，以提供有关金属配体相互作用的信息。通过对固体核磁共振光谱、x射线吸收光谱、紫外光电子能谱等方法的详细分析，再加上与最新理论方法（如DFT、CCSD(T)等）的互补分析，我们将能够直接探测与催化直接相关的有机金属配合物的电子结构。最初的重点将是研究先前在约克制备的偏乙烯基和炔基配合物，但随后将这些研究扩展到基础和/或应用兴趣的分子。

Transition-metal organometallic complexes play a pivotal role in a wide variety of applications. They are used from megaton scales for polymer synthesis to milligram scales for drug discovery in the pharmaceutical industry. In addition, recent work has explored the use of organometallics in materials chemistry (e.g. OLED materials) and in healthcare, as novel therapeutic agents. One of the much-lauded advantages of organometallic complexes is the ability to develop structure-activity relationships based on systematic changes to the steric and electronic properties of the ligands. These can in principle be used to inform the design of new metal complexes with advantageous properties for new or existing applications.In order to quantify the effects of changing co-ligands within the coordination sphere of the metal, a number of metrics have been devised, perhaps most famously by Tolman in the 1970s. In these studies a given spectroscopic parameter (such as the stretching frequency of a carbonyl ligand) is chosen as a reporting group for these electronic changes at the metal. By recording the IR spectrum, for example, of a series of compounds it is argued that the effects on the electron density at a metal caused by a co-ligand may be evaluated. More modern approaches have focussed on a multi-parameter approach to this problem, however, a common theme is that analytical data from a co-ligand is used as reporter. Therefore, all such methods are by definition indirect measures of ligand effects and there are many examples in which the nature of ligand effects may vary depending on the reporter complex used. Therefore, in many cases our understanding of metal-ligand interactions is indirect, We propose to explore new methods to directly quantify ligand effects in organometallic chemistry which will not rely on the preparation of reporter complexes but will involve measurements directly on the metal or ligand of interest. In order to achieve this, we will employ a combination of a number of different spectroscopic and analytic methods which are rarely used in organometallic chemistry to provide information about metal-ligand interactions. By using detailed analysis of methods such as solid-state NMR spectroscopy, X-ray Absorbance Spectroscopy, and Ultra-violet photoelectron spectroscopy, coupled with complementary analysis with the latest theoretical methods (e.g. DFT, CCSD(T) etc) we will be able to directly probe the electronic structure of organometallic complexes which are of direct relevance to catalysis.The initial focus will be to study the vinylidene and alkynyl complexes previously prepared in York, but then to extend these studies to molecules of both fundamental and/or applied interest.