Uncatalyzed Hydroamination of Electrophilic Organometallic Alkynes: Fundamental,Theoretical, and Applied Aspects

Simple reactions of the most used functional groups allowing two molecular fragments to link under mild, sustainable conditions are among the crucial tools of molecular chemistry with multiple applications in materials science, nanomedicine, and organic synthesis as already exemplified by peptide synthesis and “click” chemistry. We are concerned with redox organometallic compounds that can potentially be used as biosensors and redox catalysts and report an uncatalyzed reaction between primary and secondary amines with organometallic electrophilic alkynes that is free of side products and fully “green”. A strategy is first proposed to synthesize alkynyl organometallic precursors upon addition of electrophilic aromatic ligands of cationic complexes followed by endo hydride abstraction. Electrophilic alkynylated cyclopentadienyl or arene ligands of Fe, Ru, and Co complexes subsequently react with amines to yield trans‐enamines that are conjugated with the organometallic group. The difference in reactivities of the various complexes is rationalized from the two‐step reaction mechanism that was elucidated through DFT calculations. Applications are illustrated by the facile reaction of ethynylcobalticenium hexafluorophosphate with aminated silica nanoparticles. Spectroscopic, nonlinear‐optical and electrochemical data, as well as DFT and TDDFT calculations, indicate a strong push–pull conjugation in these cobalticenium– and Fe– and Ru–arene–enamine complexes due to planarity or near‐planarity between the organometallic and trans‐enamine groups involving fulvalene iminium and cyclohexadienylidene iminium mesomeric forms.     

Deprotonative metalation using ate compounds: synergy, synthesis, and structure building

Historically, single-metal organometallic species such as organolithium compounds have been the reagents of choice in synthetic organic chemistry for performing deprotonation reactions. Over the past few years, a complementary new class of metalating agents has started to emerge. Owing to a variable central metal (magnesium, zinc, or aluminum), variable ligands (both in their nature and number), and a variable second metallic center (an alkali metal such as lithium or sodium), "ate" complexes are highly versatile bases that exhibit a synergic chemistry which cannot be replicated by the homometallic magnesium, zinc, or aluminum compounds on their own. Deprotonation accomplished by using these organometallic ate complexes has opened up new perspectives in organic chemistry with unprecedented reactivities and sometimes unusual and unpredictable regioselectivities.     

金属配合物和一氧化碳的反应

一氧化碳是发展可持续化学经济的重要原料。人们希望能够将一氧化碳催化转变成高附加值化学品,从而减少石油等化石资源对人类的束缚。研究均相金属配合物与一氧化碳的反应能够使人们了解一氧化碳转变及利用机理,并开发新催化剂高效地利用一氧化碳资源。本文从金属配合物与一氧化碳反应的活性点出发,分别讨论不同类型的金属配合物与一氧化碳的反应,以求让人们在分子水平上了解一氧化碳的基本反应原理;并总结了该领域存在的难点问题,展望了未来,希望更多的科研工作者投入其中,从而实现利用一氧化碳合成出各种各样的化学品和材料。     

Methods for the Synthesis of μ-Hydrocarbon Transition Metal Complexes without Metal–Metal Bonds

Transition metal complexes in which hydrocarbons serve as σ,σ-, σ,π- or π,π-bound bridging ligands are currently of great interest. This review presents efficient and directed syntheses for such compounds, which often have very aesthetic structures. These reactions are among the most important reaction types in modern organometallic chemistry. They can be a useful aid for the synthesis of tailor-made compounds, for example, for models of catalytic processes and, specifically, for the construction of heterometallic compounds. We will discuss reactions of electrophilic complexes with nucleophilic ones, numerous transformations of (functionalized) hydrocarbons with metal complexes, the currently very topical complexes with bridging acetylide and carbide ligands, and organometallic polymers, which can be expected to have interesting and novel materials properties. Chisholm

1 M. H. Chisholm, Polyhedron 1988 , 7, 757–1077.

has described the importance of these complexes as follows: “Central to the development of polynuclear and cluster chemistry are bridging ligands and central to organometallic chemistry are metal–carbon bonds. Thus bridging ligands hold a pivotal role ins the development of Binuclear and polynuclear organometallic chemistry”.     

Organometallic Ionic Liquids Containing Sandwich Complexes: Molecular Design,Physical Properties,and Chemical Reactivities

Ionic liquids (ILs) are salts with low melting points and are useful as electrolytes and solvents. We have developed ILs containing cationic metal complexes, which form a family of functional liquids that exhibit unique physical properties and chemical reactivities originating from metal complexes. Our study explores the liquid chemistry in the field of coordination chemistry, where solid-state chemistry is currently the main focus. This review describes the molecular design, physical properties, and reactivities of organometallic ILs containing sandwich or half-sandwich complexes. This paper mainly covers stimuli-responsive ILs, whose magnetic properties, solvent polarities, colors, or structures change by the application of external fields, such as light, heat, and magnetic fields, or by reaction with coordinating molecules.     

Medicinal Organometallic Chemistry: Designing Metal Arene Complexes as Anticancer Agents

The field of medicinal inorganic chemistry is rapidly advancing. In particular organometallic complexes have much potential as therapeutic and diagnostic agents. The carbon‐bound and other ligands allow the thermodynamic and kinetic reactivity of the metal ion to be controlled and also provide a scaffold for functionalization. The establishment of structure–activity relationships and elucidation of the speciation of complexes under conditions relevant to drug testing and formulation are crucial for the further development of promising medicinal applications of organometallic complexes. Specific examples involving the design of ruthenium and osmium arene complexes as anticancer agents are discussed.     

Manganese(II): the black sheep of the organometallic family

The organometallic chemistry of manganese in the +2 oxidation state is distinct from the organometallic chemistry of a 'typical' transition metal due to a significant ionic contribution to the manganese(II)-carbon bonds. The reduced influence of covalency and the 18-electron rule result in organomanganese(II) cyclopentadienyl, alkyl and aryl complexes possessing reactivity and structural diversity that is unique in organotransition metal chemistry. Recently, this unusual reactivity has resulted in a range of novel applications in selective organometallic and organic synthesis, and polymerization catalysis. This tutorial review summarizes key milestones in the development of manganese(II) organometallics and discusses how some of their current synthetic applications have evolved from many fascinating fundamental studies in the area.     

Stoichiometric and catalytic reactivity of organometallic fragments supported on inorganic oxides

The reaction of some organometallic complexes with the surfaces of inorganic oxides leads to the formation of surface organometallic complexes, chemically bound to the surface yet retaining many features of their molecular structure. These surface organometallic complexes can therefore be considered to belong to both the molecular and solid states. In cases where such complexes have been structurally characterised, their reactivity can be interpreted with molecular concepts. In this review article, the stoichiometric and catalytic reactivity of some relatively well-defined surface organometallic fragments is surveyed. Many elementary steps which have precedent in molecular organometallic chemistry and homogeneous catalysis have now been demonstrated with surface organometallic fragments, including reversible ligand binding, oxidative addition, reductive elimination, protonation, heterolytic metal—carbon bond cleavage, electrophilic CH bond activation and insertion into metal—carbon bonds. In some cases, the supported organometallic complexes are highly effective low temperature catalysts, a phenomenon which is not always observed with molecular analogues nor with conventionally prepared heterogeneous catalysts. Applications of surface organometallic chemistry to catalytic alkane hydrogenolysis, olefin isomerisation and hydrogenation, the Fischer—Tropsch synthesis and the water—gas shift reaction are discussed. Proposed mechanisms for several representative catalytic cycles are presented.     

Methyl Complexes of the Transition Metals

Organometallic chemistry can be considered as a wide area of knowledge that combines concepts of classic organic chemistry, that is, based essentially on carbon, with molecular inorganic chemistry, especially with coordination compounds. Transition‐metal methyl complexes probably represent the simplest and most fundamental way to view how these two major areas of chemistry combine and merge into novel species with intriguing features in terms of reactivity, structure, and bonding. Citing more than 500 bibliographic references, this review aims to offer a concise view of recent advances in the field of transition‐metal complexes containing M?CH₃ fragments. Taking into account the impressive amount of data that are continuously provided by organometallic chemists in this area, this review is mainly focused on results of the last five years. After a panoramic overview on M?CH₃ compounds of Groups 3 to 11, which includes the most recent landmark findings in this area, two further sections are dedicated to methyl‐bridged complexes and reactivity.     

Protonation of Unsaturated Hydrocarbon Ligands: Regioselectivity,Stereoselectivity, and Product Specificity

Understanding the mechanisms of protonation of hydrocarbon ligands is fundamental to a wide range of chemistry including organic synthesis, organometallic chemistry, and even bioinorganic chemistry. Protonation at carbon or metal sites is often slow, with the result that in species containing both types of sites, initial protonation can be at either the metal or the carbon. This has fundamental consequences on the reactivity of hydrocarbon ligands, which are highlighted in this article. In particular, many reactions are apparently the result of a regioselective protonation on the basis of structural analysis of the isolated products. In fact, these products are often formed by an indirect route involving kinetically controlled protonation at the “wrong” site followed by rearrangement to form the thermodynamically controlled, apparently regioselective, product. Other aspects of the protonation mechanisms of complexes containing hydrocarbon ligands are discussed, with an emphasis on the manner in which competitive protonation at metal or ligand can be exploited to select which hydrocarbon is produced and to control the stereochemistry of the hydrocarbon.     

A personal account of some dinitrogen and organometallic chemistry research at the University of Sussex

This article reviews the development of dinitrogen chemistry and some associated organometallic chemistry at the University of Sussex with which the author was directly involved. The establishment of the basic heavy-element halide phosphine chemistry laid the ground for the discovery of dinitrogen complexes of rhenium, osmium, molybdenum and tungsten. From there, some of the first well-defined reactions of coordinated dinitrogen (especially protonation and alkylation) were discovered and the essential mechanisms of such reactions were established. This allowed the development of models for the action of nitrogenases that are still probably the best available. Later work has produced similar models in iron chemistry and a range of organometallic chemistry has been uncovered in the effort to discover parallels between the basic organometallic chemistry of substances such as metal carbonyls, dinitrogen complexes and hydrides in their interactions with acetylenes and cyclpropene.     

Role of Ab Initio Calculations in the Design and Development of Organometallic Lanthanide‐Based Single‐Molecule Magnets

Single‐molecule magnets based on lanthanides are very attractive due to their potential applications proposed in the area of microelectronic devices. Very recent advances in this area are due to the blend of conventional lanthanide chemistry with organometallic ligands, and several breakthrough achievements are attained with this combination. Ab initio methods based on multi‐reference CASSCF calculations are playing a vital role in the design and development of such molecules. In this minireview, we aim to appraise various contributions in the area of organometallic lanthanide complexes (those containing lanthanide‐carbon bonds) and describe how these robust wavefunction‐based methods have played a constructive role not only in rationalizing the observed magnetic properties but also proven to be a potential predictive tool with some selected examples.     

New Vistas in N‐Heterocyclic Silylene (NHSi) Transition‐Metal Coordination Chemistry: Syntheses,Structures and Reactivity towards Activation of Small Molecules

This account is a review on the synthesis and transition‐metal coordination chemistry of N‐heterocyclic silylenes (NHSi’s) over the last 20 years till the present time (2012). Recently, fascinating and novel synthetic methods have been developed to access transition‐metal–NHSi complexes as an emerging class of compounds with a wealth of intriguing reactivity patterns. The striking influence of coordinating NHSi’s to transition‐metal complex fragments affording different reactivities to the “free” NHSi is a connecting theme (“leitmotif”) throughout the review, and highlights the potential of these compounds which lie at the interface of contemporary main‐group and classical organometallic chemistry towards new molecular catalysts for small‐molecule activation.     

Applications of laser ionization/fourier-transform mass spectrometry to the study of metal ions and their clusters in the gas phase

Recent software and hardware modifications of the Nicolet FTMS-1000 Fourier-transform mass spectrometer have made it possible to conduct research in what can be termed a “complete gas-phase chemical laboratory”. Selected ions of interest can be mixed with various reagents and their detailed chemistries monitored through a series of as many as eight reaction sequences. At any point in these sequences, ion structures can be elucidated and fundamental kinetic and thermodynamic parameters of the reactions can be determined. These powerful new techniques have been applied to examine the gas-phase chemistry and photochemistry of metal ions, metal ion clusters, and metal ion complexes, all of which have a bearing on the fundamentals of organometallic chemistry and catalysis.     

Anhydrous scandium, yttrium, lanthanide and actinide halide complexes with neutral oxygen and nitrogen donor ligands

Studies on lanthanide and actinide halide complexes with neutral O- and/or N-donor ligands have intensified in recent years due to their implications in homogeneous catalysis, magnetic and optical materials, as synthons for the synthesis of novel coordination and organometallic compounds and, for Ln(II) halide complexes, as reducing agents in organic synthesis. Synthetic strategies, structural diversity as well as some important properties and reactivities of these anhydrous metal (including scandium and yttrium) halide complexes are reviewed here. These complexes also hold potential as starting materials for constructing more sophisticated heterometallic assemblies by crystal engineering; the compounds of this class, either discrete ion-pairs or coordination polymers, being discussed separately under the heading heterometallic lanthanide and actinide halide complexes. The aim of this article is to provide a reference text for the researchers working in the lanthanide and actinide coordination chemistry field and to identify and signify the area of future research.     

Organometallic Aspects of the Fischer-Tropsch Synthesis

The Fischer-Tropsch Synthesis counts among the industrial-scale processes having a versatile and broad product range, and has for decades offered the most attractive possibility for the use of coal as a source of heating oil and fuels. This conceivably simple reaction, the catalytic hydrogenation of carbon monoxide, generally leads to simple hydrocarbons as well (i.e. short chain olefins) that have been sought as chemical feedstocks since the oil crisis of the seventies, but fails to provide the large-scale, economic process required, due in large part to the minimal selectivity of traditional Fischer-Tropsch processes. In an effort to solve this problem current research in this sector is concerned not only with the optimization of old and the development of new catalytic systems, but also increasingly with the elucidation of numerous relevant reaction mechanisms. This article will discuss, from the viewpoint of an organometallic chemist, the significance of typical model reactions, both with regard to some fundamental aspects of synthesis gas chemistry, and in comparison with previous views concerning the mechanism of the Fischer-Tropsch Synthesis. The importance of various unique classes of complexes that have been studied in the context of Fischer-Tropsch chemistry is also evaluated with regard to their importance in the synthesis of hydrocarbons from carbon monoxide and hydrogen. It emerges that the primary steps of the reductive oligomerization of carbon monoxide are best described by the carbide/methylene mechanism, as originally proposed by Hans Fischer and Franz Tropsch.     

芳基钌抗癌化合物的研究进展

无机药物化学领域正在快速发展,尤其是有机金属配合物作为癌症的治疗和诊断试剂有很大的潜力.芳基钌配合物中芳基对抗癌活性有重要影响,并能调控配合物金属中心的热力学和动力学性能.配合物的构效关系研究,对进一步合理设计/合成具有潜在药用价值的有机金属配合物至关重要.本文选取钌芳基配合物作为抗癌药物的具体实例进行讨论,重点介绍了多种芳基钌配合物的构效关系及抗癌机理.     

Metallogels from Coordination Complexes,Organometallic, and Coordination Polymers

A supramolecular gel results from the immobilization of solvent molecules on a 3D network of gelator molecules stabilized by various supramolecular interactions that include hydrogen bonding, π–π stacking, van der Waals interactions, and halogen bonding. In a metallogel, a metal is a part of the gel network as a coordinated metal ion (in a discrete coordination complex), as a cross‐linking metal node with a multitopic ligand (in coordination polymer), and as metal nanoparticles adhered to the gel network. Although the field is relatively new, research into metallogels has experienced a considerable upsurge owing to its fundamental importance in supramolecular chemistry and various potential applications. This focus review aims to provide an insight into the development of designing metallogelators. Because of the limited scope, discussions are confined to examples pertaining to metallogelators derived from discrete coordination complexes, organometallic gelators, and coordination polymers. This review is expected to enlighten readers on the current development of designing metallogelators of the abovementioned class of molecules.     

Steuerliganden für Katalysatoren

Ever since the isolation of the first free N‐heterocyclic carbene more than 20 years ago, this ligand class has become essential in modern chemistry. This development is decisively owed to the stability of the metal‐carbon bond, the smooth fine‐tuning of ligand properties, and the facile synthetic access to such complexes. Acting as steering ligands, they are integral parts of many organometallic compounds that currently push the frontiers of chemistry in many areas, for example the synthesis and application of immobilized, water soluble, or asymmetric systems that act as efficient catalysts in organic transformations. Additionally, metal NHC complexes find promising applications in fields beyond catalysis, such as medicine, optics, and material science.     

Large Isotope Effects in Organometallic Chemistry

The kinetic isotope effect (KIE) is key to understanding reaction mechanisms in many areas of chemistry and chemical biology, including organometallic chemistry. This ratio of rate constants, k_H/k_D, typically falls between 1–7. However, KIEs up to 105 have been reported, and can even be so large that reactivity with deuterium is unobserved. We collect here examples of large KIEs across organometallic chemistry, in catalytic and stoichiometric reactions, along with their mechanistic interpretations. Large KIEs occur in proton transfer reactions such as protonation of organometallic complexes and clusters, protonolysis of metal–carbon bonds, and dihydrogen reactivity. C−H activation reactions with large KIEs occur with late and early transition metals, photogenerated intermediates, and abstraction by metal-oxo complexes. We categorize the mechanistic interpretations of large KIEs into the following three types: (a) proton tunneling, (b) compound effects from multiple steps, and (c) semi-classical effects on a single step. This comprehensive collection of large KIEs in organometallics provides context for future mechanistic interpretation.