Photoactivation of Ruthenium Olefin Metathesis Initiators

Ben‐Asuly, Amos; Aharoni, Anna; Diesendruck, Charles E.; Vidavsky, Yuval; Goldberg, Israel; Straub, Bernd F.; Lemcoff, N. Gabriel

doi:10.1021/om9004302

Cited by 115 publications

(90 citation statements)

References 41 publications

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“…From the results we suspected that substitution of benzylidene ring in a position adjacent to the vinyl group influences mechanism of the ligand‐exchange process. In a search for the missing trans ‐Cl 2 isomers complexes cis ‐ 7 b – d were irradiated with UV light (366 nm), a technique used earlier for cis ‐to‐ trans ‐Cl 2 isomerizations 9a. In the mixtures we detected formation of small amounts of products (expectedly trans ‐Cl 2 isomers), which remained stable under ambient conditions and only slowly decayed, as detected by 1 H NMR 11.…”

Section: Methodsmentioning

confidence: 90%

The Key Role of the Nonchelating Conformation of the Benzylidene Ligand on the Formation and Initiation of Hoveyda–Grubbs Metathesis Catalysts

Bieszczad

Barbasiewicz

2015

Chemistry A European J

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Experimental studies of Hoveyda-Grubbs metathesis catalysts reveal important consequences of substitution at the 6-position of the chelating benzylidene ligand. The structural modification varies conformational preferences of the ligand that affects its exchange due to the interaction of the coordinating site with the ruthenium center. As a consequence, when typical S-chelated systems are formed as kinetic trans-Cl2 products, for 6-substituted benzylidenes the preference is altered toward direct formation of thermodynamic cis-Cl2 isomers. Activity data and reactions with tricyclohexylphosphine (PCy3 ) support also a similar scenario for O-chelated complexes, which display fast trans-Cl2 ⇄cis-Cl2 equilibrium observed by NMR EXSY studies. The presented conformational model reveals that catalysts, which cannot adopt the optimal nonchelating conformation of benzylidene ligand, initiate through a high-energy associative mechanism.

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Section: Methodsmentioning

confidence: 90%

The Key Role of the Nonchelating Conformation of the Benzylidene Ligand on the Formation and Initiation of Hoveyda–Grubbs Metathesis Catalysts

Bieszczad

Barbasiewicz

2015

Chemistry A European J

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“…Whereas Dixneuf and co-workers used [Ru(p-cymene)Cl 2 NHC] to catalyze both the RCM of dienes and also the CM of styrenes, [67] Lemcoff and coworkers described Ru-NHC complexes carrying a chelating carbene-sulfide ligand to catalyze RCM of dienes and ROMP of various cyclic olefins. [68] In both cases, irradiation caused improved catalytic performance. In the first case, light most likely induces p-cymene ligand dissociation, whereas in the latter case, irradiation induces a structural rearrangement associated with the generation of a vacant coordination site by breaking the Ru À S bond.…”

Section: Angewandte Chemiementioning

confidence: 98%

Artificial Light‐Gated Catalyst Systems

2010

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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.

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“…This reasoning was supported by GPC analysis. Lemcoff and co‐workers extended their investigations also on UV‐triggered processes and synthesized more recently several bi‐ and tridentate S ‐chelating alkylidenes, which were either very stable or more easily activated, depending on the chelating structure ( 61 ) …”

Section: Metathesis‐derived Polymersmentioning

confidence: 99%

Latent and Delayed Action Polymerization Systems

Naumann

Buchmeiser

2014

Macromol. Rapid Commun.

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Various approaches to latent polymerization processes are described. In order to highlight recent advances in this field, the discussion is subdivided into chapters dedicated to diverse classes of polymers, namely polyurethanes, polyamides, polyesters, polyacrylates, epoxy resins, and metathesis-derived polymers. The described latent initiating systems encompass metal-containing as well as purely organic compounds that are activated by external triggers such as light, heat, or mechanical force. Special emphasis is put on the different chemical venues that can be taken to achieve true latency, which include masked N-heterocyclic carbenes, latent metathesis catalysts, and photolatent radical initiators, among others. Scientific challenges and the advantageous application of latent polymerization processes are discussed.

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Photoactivation of Ruthenium Olefin Metathesis Initiators

Cited by 115 publications

References 41 publications

The Key Role of the Nonchelating Conformation of the Benzylidene Ligand on the Formation and Initiation of Hoveyda–Grubbs Metathesis Catalysts

The Key Role of the Nonchelating Conformation of the Benzylidene Ligand on the Formation and Initiation of Hoveyda–Grubbs Metathesis Catalysts

Artificial Light‐Gated Catalyst Systems

Latent and Delayed Action Polymerization Systems

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