Solid-state molecular Organometallic Chemistry of Group 7 Carbonyls: Taming Reactive Complexes in an Anionic Cage

背景：有机金属的合成，反应性和催化几乎总是在溶液中进行，其中络合物或催化剂溶解在选择的溶剂中。虽然这很方便，但通常意味着在催化过程中非常活跃的中间体或合成中的配合物很难观察，更不用说分离了，因为溶剂经常与金属中心结合或发生不可逆反应。Weller小组最近开发了一种避免溶剂结合的技术，从而分离、表征和研究了传统溶液途径无法制造的高活性复合物。该技术看似简单：所有的化学、表征、反应性甚至催化都是在单晶到单晶的转化过程中进行的，其中气体穿透晶体并与金属中心反应产生目标复合体，或者进行感兴趣的催化转化。我们称之为固态分子有机金属化学（SMOM-Chem）。例如，这种方法允许合成阳离子西格玛-烷烃配合物，这是C-H活化过程中的关键但通常是短暂的中间产物。稳定的“纳米反应器”[BArF4]-阴离子围绕在晶格中的活性阳离子周围（类似于酶的活性位点）是关键。这种方法的力量被证明是在克尺度上合成的这种烷烃配合物，在室温下是无限稳定的，而在-100摄氏度的温度和毫克的量下，溶液的寿命（最多）是几分钟。因此，SMOM技术允许隔离“不可能”的复合物。目的：到目前为止，这种化学反应主要集中在9族配合物上。问题是，SMOM化学是否可以扩展到其他过渡金属，是否可以开发出非常活泼、具有合成挑战性和催化性的系统？我们将在一个令人兴奋的新项目中回答这个问题，该项目将SMOM技术与7族阳离子（Mn, Re）结合使用光物理方法来生成和询问活性金属中心。实验方法：最近已经确定了稳定的smm系统的设计主题。根据这些标准，将合成新的阳离子Mn-或re -羰基配合物，并研究它们在固态中的反应性，例如[M（螯合配体）（CO）n][BArF4]。各种各样的配体基序（螯合，钳形，非无害配体）将用于生成新的7族SMOM系统库。这些可能已经是协调不饱和的（agostic），或者，独特的是，可以通过使用光解的co损失在原位激活。这些复合物本身就是令人着迷的，它们具有16或14个电子的高活性，可以在固/气过程中进行反应，也可以作为传统溶液过程的“插入式”催化剂。除了这些体系的基本结构键之外，还有许多反应性需要探索，例如烷烃，H2和稀有气体配合物，碳氢活化和固体/气体催化（例如醇的加氢，脱氢，异构化）。它也为使用时间分辨红外光谱研究固态内的事件提供了机会（Lynam是该领域的专家）。新颖性：基团7配合物的固态分子化学及其光物理性质的研究是新颖的；并将产生高影响力的出版物。它将突破smm化学的极限，开发新的化学（smm -光化学），并有可能解锁新的催化系统。它将3d金属化学带向了一个新的方向。培养方向：该博士生将成为有机金属合成、核磁共振（溶液和固态）、x射线晶体学和光物理新技术方面的专家。将有很多机会探索固体/气体催化。

Background: Organometallic synthesis, reactivity and catalysis is nearly always performed in the solution phase, where the complex, or catalyst, of interest is dissolved in a solvent of choice. While this is convenient it often means that very reactive intermediates in catalysis, or complexes in synthesis, are challenging to observe, let alone isolate, as the solvent often binds, or irreversibly reacts, with the metal centre. The Weller group has recently developed a technique to avoid solvent binding, and thus isolate, characterise and study highly reactive complexes that cannot be made by traditional solution routes. The technique is deceptively simple: all the chemistry, characterisation, reactivity and even catalysis is carried out in single-crystal to single-crystal transformations in which gases penetrate the crystal and react with the metal centre to generate the target complex, or undergo the catalytic transformation of interest. We term this solid-state molecular organometallic chemistry (SMOM-Chem). For example this approach allows for cationic sigma-alkane complexes to be synthesised, key - but normally transient - intermediates in C-H activation process. A stabilising "nanoreactor" of [BArF4]- anions around a reactive cation in the crystal lattice (similar to enzyme reactive sites) is key to this. The power of this approach is demonstrated by the synthesis on gram scale of such alkane complexes that are indefinitely stable at room temperature, whereas in solution lifetimes are (at best) minutes at temperatures of -100 degrees C and mg quantities. SMOM techniques thus allow for the isolation of "impossible" complexes.Objectives: Up until now this chemistry has focussed on group 9 complexes. The question is can SMOM chemistry be extended to other transition metals, and can very reactive, synthetically challenging, and catalytically interesting, systems be developed? We will answer this in an exciting new project that combines SMOM techniques with group 7 cations (Mn, Re) using photophysical methods to generate and interrogate the reactive metal centres. Experimental Approach: Very recently the design motifs for stable SMOM systems has been determined. Informed by these criteria new cationic Mn- or Re-carbonyl complexes will be synthesised and their reactivity studied in the solid-state, e.g. [M(chelating-ligand)(CO)n][BArF4]. A wide variety of ligand motifs (chelate, pincer, non-innocent ligands) will be used to generate a library of new group-7 SMOM systems. These may already be coordinatively unsaturated (agostic) or, uniquely, can be activated in situ by CO-loss using photolysis. These will be fascinating complexes in their own right, being highly reactive 16 or 14-electron species that are primed for reactivity in solid/gas processes, as well as "drop-in" catalysts for traditional solution processes. In addition to the fundamental structure bonding in these systems there is much reactivity to explore, e.g. alkane, H2 and noble-gas complexes, C-H activation and solid/gas catalysis (e.g. hydrogenation, dehydrogenation of alcohols, isomerisation). It also opens the opportunity to study events within the solid-state using time-resolved infra-red spectroscopy (Lynam is an expert in the area). Novelty: The study of solid-state molecular chemistry of group-7 complexes, and their photophysical properties, is novel; and will result in high-impact publications. It will push the boundaries of what is achievable in SMOM chemistry, develop new chemistry (SMOM-photochem) and potentially unlock new catalytic systems. It takes 3d-metal chemistry in a new direction.Training: The PhD student will become expert in organometallic synthesis, NMR (solution and solid-state), x-ray crystallography and new photophysical techniques. There will be plenty of opportunities to explore solid/gas catalysis.