Organotransition Metal Compounds Research Articles

Charge-transfer excited states in phosphorescent organo-transition metal compounds: a difficult case for time dependent density functional theory?

A series of 17 platinum(ii) and iridium(iii) complexes have been investigated theoretically and experimentally to elucidate the charge-transfer character in emission from the lowest triplet state. TDDFT is found to be surprisingly accurate.

サンドイッチ型多核金属錯体の創製

Recent development in the chemistry of multinuclear sandwich compounds is summarized in this article. Existence of stable multinuclear sandwich complexes was proven through isolation and structural characterization of a series of multinuclear palladium sandwich complexes. One-dimensional multinuclear sandwich complexes in which two parallel unsaturated hydrocarbon ligands flank a Pd chain were prepared in a size selective manner. Moreover, two-dimensional multinuclear sandwich complexes which contain a Pd sheet between two unsaturated hydrocarbon ligands were also prepared by employing mono- and polycyclic aromatic hydrocarbons as the facially coordinated ligands. Unique behavior of the multinuclear sandwich compounds such as the sliding of the bridging ligands was also revealed. These findings lead to new aspects in the structures of organotransition metal compounds.

Agostic interactions in transition metal compounds

The impact of agostic interactions (i.e., 3-center-2-electron M-H-C bonds) on the structures and reactivity of organotransition metal compounds is reviewed.

Catalysis by organotransition metal compounds: Synergism between the pure and the applied1

The modern era of transition-metal-catalyzed polymerization of alkenes began with the Nobel Prize winning work of Ziegler and Natta in the 1950s, but the field has exploded since the mid-1980s and anticipated applications of organometallic catalysts are being spectacularly realized. Our research in metal-catalyzed alkene polymerization began about ten years ago with an investigation of the catalytic applications of half-sandwich complexes of the Group 4 metals, and this lecture will describe our efforts to find both better initiators to make known commercial polymers and new initiators to make novel polymeric materials. Good luck, bad luck, blind alleys, and serendipity have all played key roles in our research, resulting ultimately in a very satisfying convergence of the motives for pure, and the needs of applied, research.Key words: alkene, polymerization, Ziegler, catalysis, carbocationic, titanium.

Polymer–Ferrocene Conjugates Containing an Ester Function in the Connecting Links

Ferrocene, the parent of the metallocene family of organotransition metal compounds, has come to occupy a significant niche in cancer research. Developmental work in the authors' laboratory has been focused on the synthesis of antiproliferative ferrocene conjugates in which the bioactive ferrocene unit is covalently, yet bioreversibly bound (anchored) to water-soluble carrier polymers designed in accordance with requisite biomedical specifications. The anchoring link in most of these conjugates has been an aliphatic spacer containing the biofissionable amide group. In this communication the synthesis of a class of ferrocene conjugates is reported in which the ferrocene group is carrier-anchored through spacers containing an ester link, of interest here because of potentially different drug release behavior. The carriers are polyamides equipped with variously spaced hydroxyl side groups, to which the ferrocenylation agent, 4-ferrocenylbutanoic acid, is connected through esterification. The coupling reactions, mediated by carbodiimide agent and catalyzed by 4-(dimethylamino)pyridine, are carried out in DMF at temperatures not exceeding 65°C, and the water-soluble product polymers are isolated in yields of typically 70–85% by precipitation, aqueous dialysis, and freeze-drying. With the molar feed ratios chosen in these coupling experiments, the incorporation of ferrocene, assessed by 1H NMR spectroscopy, corresponds to iron contents of roughly 2.5–5.5%, by mass. The conjugates will be included in a forthcoming bioactivity screening program.

Metal Complexes of Biologically Important Ligands, XCl. Introduction of Organometallic Fragments into α-Amino Acids by Reactions of α-Bromoglycine Derivatives with Anionic Organotransition-Metal Compounds

The reactions of protected α-bromoglycine esters R1(O)CNHCH(Br)CO2R2 (R1Ph, OCMe3; R2 Me, tBu) with organometallic anions of acetylferrocene, CpFe(CO)(PPh3)-C(O)CH3, (OC)5MC(OMe)CH3 (MCr, W), (OC)3Cr(η6-diphenylmethane), (OC)3Cr[η6-fluorene), (OC)3Cr(η6-dihydroanthracene) and of (OC)3Cr(-η6aniline) and (OC)3Cr(η6-o-toluidine) provide a method for the introduction of organometallic fragments into the side chains of α-amino acids.The complexes may be useful as markers for α-amino acids in peptides.The compound (OC))3Cr(η-o-C6H4(CH3)NHC-(H)(CO2Me)NHC(O)Ph was characterized by X-ray diffraction.

Organotransition Metal Compounds for Photonics: Syntheses and Structures of a Series of (Nitrostilbene)chromium Tricarbonyl Complexes

Organotransition Metal Compounds for Photonics: Syntheses and Structures of a Series of (Nitrostilbene)chromium Tricarbonyl Complexes

Organometallic diazo compounds

Organometallic chemistry has traditionally, by definition, been concerned with the chemistry of metalcarbon-bonded compounds. Nevertheless, there is growing interest in metal-heteroatom bonds such 88 M-N, M-O, M-S, etc., in organometallic compounds. The present article systematically summarizes the literature dealing with transition-metal organometallic compounds havingsome kind of M-N-N skeleton, here broadly classified under the generalized name organometallic “diazo” compounds. This area has not been reviewedpreviouslyasatopic, but mentioncan bemade of some earlier reviews that have discussed some of the typesof compoundsto be covered here. The mostrecent general review of inorganic complexes with miscellaneous nitrogen ligands was published in 1987.’ Others have dealt with organometallic compounds with nitrogen ligands related to reduced dinitrogen,’ aryldiazenido complexes? the N=N group,& diazoalkanesPb trimethylsilyldias,k and substituted hydrazines.‘,C There are useful theoretical papers discussing diazo ligands.6f-h In order to focus the review and to keep it to a reasonable length the discussion will be limited for the most part to the following types of ligands (where R signifies an organic group or H): diazenide (NNR), diazene (RNNR), hydrazide(1-) (NRNR2), hydrazide(2-) (NNRz), and hydrazine (hNNR2). That is to say, the article is concerned with the MNN skeleton in all conceivable permutations of bond orders, stereochemistry, and degrees of substitution in organotransition metal compounds. The simplest ‘diazo” ligand, dinitrogen, will not, however, be discussed, except in instances where a direct relation to subject of the review

Pressure tuning IR and micro-raman spectra of solid zeiseߣs salt, kp[pt(η-C2H4)Cl4], and the related dimer, [Pt(η-C2H4)Cl2]2

Pressure-tuning vibrational spectroscopy using diamond-anvil cells is now well established as a useful technique for investigating the phase-transition behavior of inorganic and organic solids. Much of our recent research has been focused on organotransition metal compounds, especially metal carbonyls. The pressure dependences (dv/dP) of the v(CO) modes provide important information on the extent of #- backbonding between the metals and the carbonyl groups. We have now extended these high-presure studies to other #-acceptor ligands, including olefins. We report here the results of a high-pressure IR and micro-Raman spectroscopic investigation of the ethylene complexes, K[Pt(η-C2H4)C13] (Zeise's salt) and the related dimeric species, [Pt(η-C2H4)C12]2- We were interested in examining the effect of high pressures on the Dewar-Chatt-Ducanson σ-/π-bonding description of the platinum-ethylene bonding. There is still considerable controversy over the relative σ- and π-contributions to the overall bonding in such metal-olefin complexes.Micro-Raman spectra of solid K[Pt(η-C2H4)C13] were obtained at room temperature for the low-energy region (500-180 cm-1) at varying pressures up to 33 kbar with the aid of a diamond-anvil cell. Similarly, pressure-tuning IR spectra were measured for Zeise's salt (3080-480 cm-1; 32 kbar) and Zeise's dimer (4000-480 cm-1; 28 kbar) up to the pressures indicated.

The systematic study of the organotransition metal compounds

This article describes an extension to classifying organometallic complexes according to the carbon-donor ligand, that may be useful to show how the various existing types of low-valence organotransition metal complexes can be constructed.

The Isolobal Theory and Organotransition Metal Chemistry—Some Recent Advances

Abstract Hoffmann's isolobal theory was largely credited for bridging the gap between inorganic complexes and carbon-based compounds. Recent advances have extended its applications to organotransition metal monomers and cluster molecules. Isolobal mapping is not only applicable among molecules and molecular fragments, but also significant in comparing organometallic reactions. Such advancement is likely to influence current trends in mechanistic chemistry. Through a concise review of some of the latest and more representative results, this article aims to highlight and illustrate the versatility and applicability of the theory. Coupled with the Polyhedral Skeletal Electron Pair theory, the isolobality principle provides a useful theoretical underpinning for some synthetic and structural characteristics of many organotransition metal compounds.

Introductory remarks

It is more than 30 years since the foundation of organo-transition metal chemistry and its useful applications. The names of Nobel Laureates E. O. Fischer and G. Wilkinson, K .Ziegler and G. Natta are associated with the earliest years of the development of this field. Indeed, the early chemistry of hydrocarbon derivatives of transition metals was largely developed by inorganic chemists whose primary interest focused on the transition metal chemistry rather than on transformations of organic compounds. Apart from a few, academic organic chemists were rather slow to appreciate the potential of organo-transition metal compounds as synthetic intermediates. What were the reasons for this delay? It was perhaps because in the early days of the development of organo-transition metal chemistry it was difficult to perceive pattern and order in the abundant complexity of new structural types and reactivities. Indeed, in the early days the fragmentary knowledge and understanding mitigated against much pretence of deeply argued strategies for research. Also, new techniques such as the need to work under an inert atmosphere with a vacuum/nitrogen line were unfamiliar to organic chemists

ChemInform Abstract: Chemistry of Organo Transition Metal Compounds. Part 52. Preparation, Characterization, and Reactions of (C5H5)3Ce·THF and Na(Ce(C5H5)4)·THF.

ChemInformVolume 19, Issue 20 Organoelement Compounds ChemInform Abstract: Chemistry of Organo Transition Metal Compounds. Part 52. Preparation, Characterization, and Reactions of (C5H5)3Ce·THF and Na(Ce(C5H5)4)·THF. K. JACOB, K. JACOB Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", DDR-4200 MerseburgSearch for more papers by this authorM. GLANZ, M. GLANZ Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", DDR-4200 MerseburgSearch for more papers by this authorK. TITTES, K. TITTES Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", DDR-4200 MerseburgSearch for more papers by this authorK.-H. THIELE, K.-H. THIELE Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", DDR-4200 MerseburgSearch for more papers by this author K. JACOB, K. JACOB Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", DDR-4200 MerseburgSearch for more papers by this authorM. GLANZ, M. GLANZ Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", DDR-4200 MerseburgSearch for more papers by this authorK. TITTES, K. TITTES Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", DDR-4200 MerseburgSearch for more papers by this authorK.-H. THIELE, K.-H. THIELE Sekt. Chem., Tech. Hochsch. "Carl Schorlemmer", DDR-4200 MerseburgSearch for more papers by this author First published: May 17, 1988 https://doi.org/10.1002/chin.198820240Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume19, Issue20May 17, 1988 RelatedInformation

Synthesis and structure of (cis)-[1-ferrocenyl-2-(4-nitrophenyl)ethylene], an organotransition metal compound with a large second-order optical nonlinearity

There is considerable interest in materials with nonlinear optical properties. Two important manifestations of light interacting with a nonlinear optical material are, the process of second-harmonic generation (SHG) which is relevant to new laser technology, and the electro-optic effect which has applications in telecommunications and in integrated optics1. Several inorganic and organic materials with unusually large second-order nonlinearities are known1. However, reports of organometallic compounds with second-order nonlinear optical properties are few2–4 and they have relatively small values for SHG efficiencies. Here we describe a new compound (cis)-[1-ferrocenyl-2-(4-nitrophenyl)ethylene] (compound 2) exhibits solvatochromic behaviour. A Kurtz-powder measurement, using 1.907 µm light from a Raman shifted Nd-YAG laser operating at 1.064 µm, shows the compound provides highly efficient second harmonic generation, with a signal some 62 times that from a urea reference sample. The single crystal X-ray structure of (cis)-[1-ferrocenyl-2-(4-nitrophenyl)ethylene] has been determined. The large nonlinear optical property of this compound demonstrates that organotransition metal compounds can play an important role in the development of the nonlinear optical properties of materials.

ChemInform Abstract: Potential Energy Profile of a Full Catalytic Cycle of Olefin Hydrogenation by the Wilkinson Catalyst.

It is only in the last few years that for elementary reactions of organotransition-metal compounds the transition-state geometry can be optimized and the potential energy profile can be obtained from ab initio molecular orbital calculations. Elementary reactions thus studied include oxidative addition/reductive elimination, olefin insertion/..beta..-elimination carbonyl insertion, thermolysis of ketene complexes, and isomerization of metallacycle to an alkylidene-olefin complex. Despite such success, a study of an entire cycle of a catalytic process, consisting of several elementary reactions, has been a challenge to theoreticians. The authors communicate here the results of the first such study, on homogeneous olefin hydrogenation by the Wilkinson catalyst. They concentrate on the dominant catalytic cycle of the mechanism proposed by Halpern. The model of the cycle they adopted, consists of oxidative addition of H/sub 2/, coordination of ethylene, ethylene insertion, isomerization, and reductive elimination of ethane.

ChemInform Abstract: Organo Transition Metal Compounds. Part 49. Reactions of Cerium(IV) Acetylacetonate with Organolithium and Organomagnesium Compounds.

AbstractDepending on the molar ratio the Ce(IV) acetylacetonate (II) reacts with Li organyls with Ce(IV) reduction to give the Li cerate (I) or the Li trialkylcerates (III).

Active MgH 2Mg-systems for hydrogen storage

Novel, highly active MgH 2-Mg-systems, which can be used both in synthetic chemistry and as high temperature hydrogen storage materials, have been studied at the Max-Planck-Institut für Kohlenforschung in Mülheim-Ruhr, West Germany, since 1978. The original preparative procedure was based on the hydrogenation of magnesium under mild conditions (20–60°C. 1–80 bar) in an organic solvent and in the presence of a soluble organo transition metal catalyst. This process yields a MgH 2 storage material with outstanding kinetic properties (w.r.t. the release and take-up of H 2 at normal pressure and 230–350°C), a high specific surface area (100–130 m 2g −1) and a high storage capacity for hydrogen (7 wt%). It suffers, however, from the disadvantage of being pyrophoric. Subsequently, MgH 2-MgH 2-storage materials have been developed using magnesium powder doped with small quantities of transition metal complexes or organotransition metal compounds and these can be safely handled in air. The new MgH 2Mg-systems can be used for hydrogen storage, hydrogen purification and separation and heat storage, provided a 300–350°C heat source is available to release the hydrogen. Their main features include low material and production costs, highly satisfactory kinetics, high hydrogen and heat capacity, relative insensitivity toward impurities in hydrogen (H 2O, O 2, CO, etc.) and stability toward air.

Behaviour of alpha-functional organotransition metal compounds : nuclear magnetic resonance investigation of a novel Friedel-Crafts metallacyclisation of halogenomethyl(arylphosphine)platinum(ii) complexes

Reaction of complexes trans-[Pt(CH2X′)XL2] with 2 equivalents of AgBF4 in the presence of triarylphosphine (L′) affords cationic metallacyclic species [Pt{PPh2(2-C6H4CH2)}L(L′)]BF4 [X = Cl, Br, or I; X′ = Cl or I; L = PPh3; L′ = PPh3 or P(C6H4Me-4)3]. When L′ = P(C6H4Me-4)3 the isomeric metallacycle [Pt(P(C6H4Me-4)2(4-MeC6H3CH2-2)}L2]BF4 is also formed in significant amount. In the absence of additional phosphine the cyclic product [Pt{PPh2(2-C6H4CH2)]L(S)]BF4 is observed instead (S = solvent molecule). This novel metallacyclisation route features a remarkably facile intramolecular electrophilic substitution by the metal-bound methylene on an aryl substituent of a co-ordinated phosphine. The extent to which this involves the incoming phosphine is controlled by the rate of isomerisation of intermediates. Multinuclear n.m.r. characteristics of the products and intermediates are reported and mechanistic implications discussed.

Carbonylation of C5H5Fe(CO)(CH3)L— a CO‐Insertion and No CH3‐Migration

The reaction of organo-transition metal compounds with CO has been investigated in the optically active iron complex (1). Unlike CH3Mn(CO)5, the complex (1) is carbonylated with stereospecific insertion of the CO group present in the molecule into the Fe—CH3 bond to give (2). The η2-acetyl complex (3) (L = PPh2NMe—(S)-CHMePh) is the most likely intermediate, also during de-carbonylation.

Organo transition metal compounds as intermediates in homogeneous catalytic reactions

Abstract