Solid-state NMR studies of supported organometallics

Solid-state nuclear magnetic resonance spectroscopy has been increasingly applied for characterization of supported organometallic complexes. Whereas early studies focused on highly mobile physisorbed species, the development of high-resolution solid-state techniques has extended NMR studies to less mobile chemisorbed complexes. In addition to identification of surface species, solid-state NMR has yielded information concerning mobility, the nature of the bonding to the surface, and even the active sites in catalytic reactions of supported organometallic complexes. When coupled with other characterization methods, NMR has proven to be an effective probe of surface organometallic structure. Solid-state NMR studies of the following systems are reviewed: ligand attached metal complexes, supported metal carbonyls and olefins, supported organoactinides and zeolite encapsulated organometallics.     

Laser photochemistry of organometallic compounds related to applications in microelectronics

Photochemistry of organometallic compounds achieves a marriage of a rich variety of organometallic chemistry and the full potential of electronically excited states of molecules. The application of lasers as light sources adds a great many new features to these studies, which cannot be attained by other means, because lasers provide light of such a high quality, e.g. a high-intensity, energetic (i.e. wavelength) purity, a high degree of coherence, and a high spatial and temporal resolution. Laser photochemistry of organometallic compounds, such as laser photochemical vapor deposition (LPCVD), laser ablation, and photochemical dry etching, forms the basis of many important industrial processes which sustain the present-day microelectronics industries. Lasers are used not only to photodissociate organometallic molecules, but to monitor the reaction steps by probing the starting material, chemical intermediate, or final product by many laser-based spectroscopic methods. Although it is a very young area of science (the first laser was operated in 1960), this research area is now really ebullient, as a result of strong interest from both the fundamental and the practical sides. Laser photochemistry of organometallic compounds extends a wide and fertile research frontier, full of challenge and novel possibilities. In the present review, the present status of laser (ultraviolet and visible) photochemistry of organometallic compounds related to these industrial applications is briefly reviewed, with special emphasis on the basic studies of the relevant photochemistry and their relationship to photochemical processes on solid surfaces.     

Assigning the ESI mass spectra of organometallic and coordination compounds

Electrospray ionization mass spectrometry (ESI‐MS) is a useful technique for solving organometallic and coordination chemistry characterization problems that are difficult to address using traditional methods. However, assigning the ESI mass spectra of such compounds can be challenging, and the considerations involved in doing so are quite different from assigning the mass spectra of purely organic samples. This is a tutorial article for organometallic/coordination chemists using ESI‐MS to analyze pure compounds or reaction mixtures. The fundamentals of assigning ESI mass spectra are discussed within the context of organometallic and coordination systems. The types of ions commonly observed by ESI‐MS are categorized and described. Finally, a step‐by‐step guide for the assignment of organometallic and coordination chemistry ESI mass spectra is provided along with two case studies.     

锕系多重键金属有机化合物研究进展

多重键金属有机化合物在多种催化反应中已经得到广泛的应用, 并取得了很好的研究成果. 目前, 多重键金属有机化合物的研究已成为催化化学领域中一个引人注目的研究热点. 综述了锕系多重键金属有机化合物的研究进展. 根据化合物多重键的不同, 分别讨论了它们的合成及反应性能, 并定性讨论了多重键的性质.     

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.     

Determination of organometallic compounds by capillar gas chromatography – inductively coupled plasma mass spectrometry

The separation and detection of volatile organometallic compounds containing tin, iron, and nickel has been achieved using capillary GC–inductively coupled plasma–mass spectrometry (capillary GC-ICP-MS). Detection limits range from 3.0 to 7.0 pg/s. The presence of volatile organotin compounds in a harbor sediment has been confirmed. The retention range of the organometallic compounds analyzed by capillary GC-ICP-MS has been extended considerably beyond that possible in earlier studies (retention indices up to 3400).     

Benzodiazepines: Drugs with Chemical Skeletons Suitable for the Preparation of Metallacycles with Potential Pharmacological Activity

The synthesis of organometallic compounds with potential pharmacological activity has attracted the attention of many research groups, aiming to take advantage of aspects that the presence of the metal-carbon bond can bring to the design of new pharmaceutical drugs. In this context, we have gathered studies reported in the literature in which psychoactive benzodiazepine drugs were used as ligands in the preparation of organometallic and metal complexes and provide details on some of their biological effects. We also highlight that most commonly known benzodiazepine-based drugs display molecular features that allow the preparation of metallacycles via C-H activation. These organometallic compounds merit further attention regarding their potential biological effects, not only in terms of psychoactive drugs but also in the search for drug replacements, for example, for cancer treatments.     

The Computational Road to Better Catalysts

Computational studies, especially those that use density functional theory (DFT), have become pervasive in the characterization, mechanistic study, and optimization of homogeneous organometallic catalysts, and the “rational” design of such catalysts seems within reach once more. But how advanced, user‐friendly, and reliable are the computational tools that are currently available? Here we summarize the current state of the art for predictive computational organometallic chemistry in reference to the different stages of catalyst development by considering characterization, mechanistic studies, fine‐tuning/optimization, and evaluation of novel designs. We also assess critically where the strengths and weaknesses of computational studies lie and hence map out the road ahead for the design and discovery of novel catalysts in silico and in combination with targeted experimental studies.     

Organometallic Allene [(μ-C)(Fe(CO)4)2]: Bridging Carbon Showing Transformation from Classical Electron-Sharing Bonding to Double σ-Donor and Double π-Acceptor Ligation

Allenes (R₂C=C=CR₂) have been traditionally perceived to feature localized orthogonal π-bonds between the carbon centres. We have carried out quantum-mechanical studies of the organometallic allenes envisioned by the isolobal replacement of the terminal CH₂ groups by the d⁸ Fe(CO)₄ fragment. Our studies have identified two organometallic allenes viz. D_2d symmetric [(μ-C)(Fe(CO)₄)₂] ( 2 ) and D₃ symmetric [(μ-C)(Fe(CO)₄)₂] ( 3 ) with trigonal bipyramidal coordination at the Fe atoms. Compound 2 features the bridging carbon atom in an equatorial position with respect to the ligands on the TM centre, while 3 features the central carbon atom in an axial position. The bis-pseudoallylic anionic delocalisation proposed in the C2-C1-C3 spine of organic allene is retained in the organometallic allene 2 , and is transformed to a typical three-centre bis-allylic anionic delocalisation in the organometallic allene 3 . The topological analysis of electron density also indicates a bis-allylic anionic type delocalisation in the organometallic allenes. The quantitative bonding analysis using the EDA-NOCV method suggests a transition from classical electron-sharing bonding between the central carbon atom and the terminal groups in 1 to donor-acceptor bonding in 3 . Meanwhile, both electron-sharing and donor-acceptor bonding models are found to be probable heuristic bonding representations in the organometallic allene 2 .     

Charge-tagged ligands: useful tools for immobilising complexes and detecting reaction species during catalysis

In recent years, charge-tagged ligands (CTLs) have become valuable tools in organometallic catalysis. Insertion of an ionic side chain into the molecular skeleton of a known ligand has become a useful protocol for anchoring ligands, and consequently catalysts, in polar and ionic liquid phases. In addition, the insertion of a cationic moiety into a ligand is a powerful tool that can be used to detect reaction intermediates in organometallic catalysis through electrospray ionisation mass spectrometry (ESI-MS) experiments. The insertion of an ionic tag ensures the charge in the intermediates independently of the ESI-MS. For this reason, these ligands have been used as ionic probes in mechanistic studies for several catalytic reactions. Here, we summarise selected examples on the use of CTLs as immobilising agents in organometallic catalysis and as probes for studying mechanisms through ESI-MS.     

Application of size exclusion chromatograph (sec) to organometallic compounds

The utility of modern size-exclusion chromatography for the separation and identification of organometallic compounds is described with examples from studies on low-valent complexes of nickel and iron.     

Dramatically Enhanced Solubility of Halide‐Containing Organometallic Species in Diiodomethane: The Role of Solvent⋅⋅⋅Complex Halogen Bonding

In the current study, we evaluated the solubility of a number of organometallic species and showed that it is noticeably improved in diiodomethane when compared to other haloalkane solvents. The better solvation properties of CH₂I₂ were associated with the substantially better σ‐hole‐donating ability of this solvent, which results in the formation of uniquely strong solvent–(metal complex) halogen bonding. The strength of the halogen bonding is attenuated by the introduction of additional halogen atoms in the organometallic species owing to the competitive formation of more favourable intermolecular complex–complex halogen bonding. The exceptional solvation properties of diiodomethane and its inertness towards organometallic species make this solvent a good candidate for NMR studies, in particular, for the acquisition of spectra of insensitive spins.     

Selective photo-deposition of Cu onto the surface of monodisperse oleic acid capped TiO2 nanorods probed by FT-IR CO-adsorption studies

A novel, non-aqueous, organometallic route to nanocomposite Cu@TiO2 materials is presented. TiO2 nanorods stabilized with oleic acid (OLA) were used as support for the photo-assisted deposition of Cu using the organometallic Cu(II) precursor [Cu(OCH(CH3)CH2N(CH3)2)2] (1). The copper precursor penetrates through the shell of OLA and is photo reduced to deposit Cu0 directly at the surface of the TiO2 rods. The obtained Cu decorated nanorods were still soluble in nonpolar organic solvents without change of the morphology of nanorods. The Cu@TiO2 colloid was characterized by means of UV-VIS, XRD, AAS, and HRTEM. FTIR CO adsorption studies provide evidence for Cu0 anchored at the titania surface by a characteristic absorption at 2084 cm-1. Comparative studies of Cu-deposition were performed using CuCl2 as simple Cu source which proved that the concept of organometallic disguise of the metal centre results in a higher reaction rate and the circumvention of non-selective reduction, parasitic side reactions and undesired agglomeration of the OLA stabilized titania nanorods.     

Fluorocarbon metal compounds—role models in organotransition metal chemistry

Early studies on organo-transition metal complexes with fluorocarbon ligands are reviewed in a historical context in relation to the renaissance of organometallic chemistry which followed the discovery of ferrocene.     

Recent synthetic applications of manganese in organic synthesis

While the organometallic compounds derived from many metals have found a broad application in organic synthesis, the use of organomanganese compounds has only recently been developed due to the passivity exhibited by commercial Mn in the direct metalation of organic compounds. In this Concept article, we highlight the potential of manganese and its organometallic compounds in organic synthesis by illustration of the studies previously reported by others and our laboratory in this field. Based on the transformations reported herein, organomanganese compounds could become important tools in the future of the organic synthesis, due to their high selectivity.     

Gmelin handbook of inorganic chemistry

IR studies show that in solution aluminium trihalides form Lewis acid adducts at the iron atom in polyolefin tricarbonyliron complexes. A ketonic organometallic compound also forms a 2:1 adduct.     

Aluminum trihalide interactions with polyolefin tricarbonyliron compounds

IR studies show that in solution aluminum trihalides form Lewis acid adducts at the iron atom in polyolefin tricarbonyliron complexes. A ketonic organometallic compound also forms a 2/1 adduct.     

新型含N-杂环卡宾二硫化碳配体的锰铼金属双核化合物的合成、表征及电化学性质简

合成了一系列含N-杂环卡宾二硫化碳加合物配体的锰铼金属有机化合物,其中包括3种单核化合物和3种双核化合物,对它们的结构进行了表征,并研究其反应性和电化学性质. 与三烷基膦二硫化碳配体相比,含N-杂环卡宾二硫化碳加合物配体的锰铼金属有机化合物展现出不同的反应特性. 研究结果表明,[MnRe(CO)6(μ-H){μ-CH3SC(S)IMes2}]配合物具有催化质子还原成氢气的能力.     

Forty years of Umpolung in organometallic chemistry: from carbanionic nucleophiles to metallic electrophiles

The evolution of mechanistic insight into the nature of organometallic reactions over the last forty years is recounted from the personal perspective of a chemist trained in the empirical tradition of organometallic chemistry. Starting from the viewpoint prevailing in the 1950s of organometallics as potential carbanionic nucleophiles, this investigator has become persuaded by his researches with Group 13 organometallics of the merits of treating these reagents as organometallic electrophiles. The profound effects that a tricoordinate boron center can exert on the structure and reactivity of boracyclopolyenes is a telling illustration of such boron electrophilicity operating in an intramolecular fashion. The elucidation of the mechanisms of both the carbalumination and the hydroalumination of olefins and acetylenes has adduced cogent evidence for the rate-determining step being the electrophilic attack of tricoordinate aluminum on the carbon-carbon π-electron cloud of the substrate. Finally, in an investigation of the molecular basis for Ziegler-Natta catalysis, the Breslow-Natta soluble catalyst for the polymerization of ethylene, Cp₂TiCl₂-R_nAlCl_3−n, was examined in detail and compelling evidence has been adduced that the active catalyst site is the solvent-separated ion-pair, [Cp₂TiR]⁺ [R_nAlCl_4−n]⁻.. Here again, the polymerization reaction is initiated by an organometallic electrophile, indeed by an even more powerful cationic electrophile. The net effect of these studies has been an Umpolung in the manner with which this chemist and many of his colleagues view organometallic reaction mechanisms.     

Development of organometallic (organo‐transition metal) pharmaceuticals

This paper is aimed at introducing the organometallic chemist to the fascinating area of organometallic pharmaceuticals. It commences by identifying the properties of organometallic (transition metal) compounds that lend themselves to medical applications. Next, the specialized techniques and methods that are used to assess the medicinal properties of compounds are summarized, and although these techniques are not restricted to organometallic compounds, all examples are concerned with organometallic compounds. The design and evaluation of organometallic compounds for medicinal applications are described in context with the diseases they have been evaluated against, and areas are identified that may have most potential for organometallic pharmaceuticals. Some new results, including the first example of an organo‐osmium compound that might exhibit effective anticancer properties, are also described. Copyright © 2005 John Wiley & Sons, Ltd.