Thermal- and photoinduced ring-opening metathesis polymerization (ROMP)/(PROMP): an efficient tool in polymer chemistry
TL;DR: In this article, the photo-induced ring-opening metathesis polymerization (ROMP) reaction with simple alkyl complexes, e.g. [W(NPh)(CH2SiMe3)3Cl] as well as [Ru(solvent)6]2+ acting as the catalytically active species are discussed.
About: This article is published in Progress in Organic Coatings.The article was published on 1997-12-01. It has received 25 citations till now. The article focuses on the topics: Ring-opening metathesis polymerisation & ROMP.
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TL;DR: This Review outlines the general concept of light-gated catalysis based on photocaged and also photoswitchable systems, and discusses relevant examples of the past and recent literature.
Abstract: Having control over an entity or even an entire process is arguably the ultimate demonstration of its understanding and it will enable its potential to be fully exploited. With this in mind, chemists have not only been creating and optimizing a myriad of different catalysts for most (relevant) chemical reactions over the past decades, but have recently started to implement controlling elements into the catalyst design. These incorporated gates operate upon exposure to suitable control stimuli, and light represents perhaps the scientifically and technologically most attractive stimulus. In principle, irradiation can thereby induce activity and selectivity in a given catalyst system with high spatial and temporal control, leading to an overall localization and amplification of an optical signal and translation into chemical action. While nature has developed and utilized this concept, in particular in the processes of vision and photomovement, such artificial photocontrolled catalyst systems offer unique opportunities and have high potential for future applications. In this Review, we outline the general concept of light-gated catalysis based on photocaged and also photoswitchable systems, and discuss relevant examples of the past and recent literature.
298 citations
TL;DR: This tutorial review aims to provide the reader with a concise overview of early breakthroughs and recent key developments in the endeavor to develop latent olefin metathesis catalysts, and to illustrate their use by prominent examples from the literature.
Abstract: Olefin metathesis is a versatile synthetic tool for the redistribution of alkylidene fragments at carbon–carbon double bonds. This field, and more specifically the development of task-specific, latent catalysts, attracts emerging industrial and academic interest. This tutorial review aims to provide the reader with a concise overview of early breakthroughs and recent key developments in the endeavor to develop latent olefin metathesis catalysts, and to illustrate their use by prominent examples from the literature.
187 citations
TL;DR: Ruthenium-based catalysts are at the center of attention because of their remarkable tolerance toward oxygen, moisture, and numerous functionalities as discussed by the authors, and their applications to the preparation of advanced polymeric materials are briefly reviewed.
Abstract: For many years, olefin metathesis has been a central topic of industrial and academic research because of its great synthetic utility. The employed initiators cover a wide range of compounds, from simple transition-metal salts to highly sophisticated and well-defined alkylidene complexes. Currently, ruthenium-based catalysts are at the center of attention because of their remarkable tolerance toward oxygen, moisture, and numerous functionalities. This article focuses on recent developments in the field of ring-opening metathesis polymerization using ruthenium-based catalysts. ruthenium-based initiators and their applications to the preparation of advanced polymeric materials are briefly reviewed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2895–2916, 2002
130 citations
TL;DR: The development of the first thermally stable, truly UV-triggerable precatalysts for ROMP and their application in surface functionalization is reported.
Abstract: Metathesis chemistry and, in the context of polymer chemistry, ring-opening metathesis polymerization (ROMP) have gained a strong position in chemistry and materials science. ROMP is strongly associated with two classes of well-defined metal alkylidene based initiators, molybdenumbased Schrock and ruthenium-based Grubbs type initiators. Despite the tremendous achievements in catalyst development, both families of initiators are still experiencing ongoing, vivid development. Most Grubbs type initiators work at room temperature or require only gentle warming to work properly. More recently, an increasing number of reports on latent Ru-based initiators has appeared. Such precatalysts are of particular interest in technical applications of ROMP, since they allow for premixing, that is, the preformulation of a monomer/precatalyst mixture, its storage over a longer period of time even at elevated temperatures (usually less than 45 8C), and, most importantly, the shaping and profiling of such mixtures prior to polymerization (“curing”). Numerous latent Grubbs type initiators have been reported recently; however, all these precatalysts are triggered thermally. By contrast, surface modification and functionalization require UV-triggerable precatalysts. Few such systems have been reported to date. The synthesis of photoactive Schrock type tungsten-based compounds as well as ruthenium and osmium arene compounds of the general formula [Ru(p-cymene)Cl2(PR3)] and [Os(p-cymene)Cl2(PR3)] (R= cyclohexyl, etc.) were first reported by van der Schaaf et al. They also investigated the photoinduced polymerization of different functionalized norbornenes and 7-oxanorbornenes using various [Ru(solvent)n]X2 complexes, (X= tosylate, trifluoromethanesulfonate) as well as Ru half-sandwich and sandwich complexes. Noels and co-workers reported on the visiblelight-induced ROMP of cyclooctene using [RuCl2(IMes)(pcymene)] (IMes= 1,3-dimesitylimidazol-2-ylidene). Some of these systems were also used in ring-closing metathesis reactions. Most of the systems available to date, however, have significant disadvantages. They either show low activity, resulting in low polymer yields (less than 30%) in the photochemically triggered process, or the irradiation wavelength necessary to trigger ROMP is 360 nm or higher. In the latter case, the initiatorsA thermal stability is generally poor, thus discouraging their application in photoinduced ROMP. Thus, none of the systems reported to date was entirely thermally stable above or even at room temperature. Therefore, these systems do not fulfill the requirements of a truly latent photocatalyst. Herein, we report the development of the first thermally stable, truly UV-triggerable precatalysts for ROMP and their application in surface functionalization. We commenced our investigations with [Ru(IMesH2)(CF3CO2)(tBuCN)4)] CF3CO2 (PI-1) and [Ru(IMes)(CF3CO2)(tBuCN)4)] CF3CO2 (PI-2), which were prepared from [Ru(CF3CO2)2(L)(p-cymene)] [31,32] (L= IMes or IMesH2, 1,3-dimesityl-4,5-diyhdroimidazolin-2-ylidene) by reaction with excess tBuCN. Both compounds can be handled in air. H and C NMR spectroscopy data and elemental analysis reveal the presence of one N-heterocyclic carbene (NHC) ligand, two inequivalent trifluoroacetate groups, and four tBuCN ligands, suggesting cationic Ru complexes. The structures of PI-1 and PI-2 were confirmed by X-ray analysis; the structure of PI-1 is shown in Figure 1 (see also the Supporting Information). Upon mixing of either PI-1 or PI-2 with monomers 3–8 (Scheme 1), no reaction was observed at room temperature within 24 h. Even highly reactive (distilled) dicyclopentadiene (4) did not react with PI-1 or PI-2 at room or elevated temperature (RT
94 citations
TL;DR: In this paper, the authors discuss the problem of bestrahlung in a katalytischen system, i.e., kontrolle uber einen Gegenstand oder einen gesamten Prozess, ist zweifelsohne der ultimative Beweis fur dessen Verstandnis.
Abstract: Kontrolle uber einen Gegenstand oder einen gesamten Prozess auszuuben, ist zweifelsohne der ultimative Beweis fur dessen Verstandnis und ermoglicht erst die vollstandige Nutzung seines Potenzials. Vor diesem Hintergrund haben Chemiker in den vergangenen Jahrzehnten fur die meisten (relevanten) chemischen Reaktionen nicht nur eine Vielzahl von Katalysatoren entwickelt und optimiert, sondern vor kurzem auch damit begonnen, Steuerungselemente in das Katalysatordesign einzufuhren. Diese integrierten Kontrolleinheiten werden durch Einwirkung geeigneter Stimuli reguliert, wobei Licht aus wissenschaftlicher und technologischer Sicht vermutlich am attraktivsten ist. Bestrahlung kann hierbei prinzipiell sowohl Aktivitat als auch Selektivitat in einem gegebenen katalytischen System mit hoher raumlicher und zeitlicher Prazision steuern, die zu einer allgemeinen Lokalisierung und Verstarkung des optischen Signals und dessen Umwandlung in chemische Aktivitat fuhrt. Wahrend in der Natur dieses Konzept bereits erfolgreich Anwendung findet, im Speziellen beim Sehprozess und bei der Photobewegung, eroffnen derartige kunstliche lichtgesteuerte katalytische Systeme einzigartige Moglichkeiten und verfugen uber ein hohes Potenzial fur zukunftige Anwendungen. In diesem Aufsatz beschreiben wir die grundsatzliche Idee der lichtgesteuerten Katalyse basierend auf photoaktivierbaren und photoschaltbaren Systemen und diskutieren relevante Beispiele aus der alteren und neueren Literatur.
93 citations
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1,357 citations
TL;DR: On propose un schema reactionnel en accord avec les faits observes dans la reaction de disproportion des olefines acycliques, la polymerisation des ollines cycliques, the telomerisation of l'olefine cyclique, and the polymerisation of olline cycliques by les olefine acyCLiques as discussed by the authors.
Abstract: La co-reaction des olefines cycliques avec les olefines acycliques en presence des systemes WOCl4/Al(C2H5)2Cl et WOCl4/Sn(C4H9)4 conduit a une telomerisation de l'olefine cyclique; aux extremites des molecules de telomere sont fixes deux groupements, identiques ou differents, issus de l'olefine acyclique par une reaction non consecutive.
Ont ete plus particulierement etudies: le cyclopentene et le cyclooctene d'une part, le pentene-2, le pentene-1, le butene-2 et le propylene d'autre part.
Le cyclooctadiene-1.5 et le cyclododecatriene-1.5.9 reagissent avec le pentene-2, par reaction non consecutive, en tant que reste CHCH2CH2CH.
La repartition des telomeres obeit a une loi statistique.
On propose un schema reactionnel en accord avec les faits observes dans la reaction de disproportion des olefines acycliques, la polymerisation des olefines cycliques et la telomerisation des olefines cycliques par les olefines acycliques.
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