Carbene insertion into transition metal–carbon bonds: a new tool for catalytic C–C bond formation

Franssen, Nicole M. G.; Walters, Annemarie J. C.; Reek, Joost N. H.; Bruin, Bas de

doi:10.1039/c0cy00065e

Cited by 89 publications

(50 citation statements)

References 87 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[1] The commercial synthesis of these materials is mainly based on radical processes, for which stereocontrol is difficult to achieve. [3] These (co)polymers reveal interesting and unexpected material properties, such as thermotropic and lyotropic liquid crystallinity, gel formation, a broad thermal stability range, and a high storage modulus up to high temperatures. However, to the best of our knowledge there are no catalysts known that can polymerize 1,2-difunctionalized olefins such as fumarates or maleates in a stereocontrolled manner.…”

mentioning

confidence: 99%

“…However, to the best of our knowledge there are no catalysts known that can polymerize 1,2-difunctionalized olefins such as fumarates or maleates in a stereocontrolled manner. Therefore, the synthesis of high molecular weight and stereoregular densely functionalized sp 3 -carbon chain (co)polymers containing a polar substituent at every carbon atom of the polymer backbone is currently restricted to the Rh-mediated carbene polymerization techniques recently developed in our group (C1 polymerization; Scheme 1). [3] These (co)polymers reveal interesting and unexpected material properties, such as thermotropic and lyotropic liquid crystallinity, gel formation, a broad thermal stability range, and a high storage modulus up to high temperatures.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Stereospecific Carbene Polymerization with Oxygenated Rh(diene) Species

et al. 2012

Self Cite

View full text Add to dashboard Cite

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Stereospecific Carbene Polymerization with Oxygenated Rh(diene) Species

et al. 2012

Self Cite

View full text Add to dashboard Cite

show abstract

“…C1 monomers) as 'functional-group carriers' in coordinationinsertion polymerisation has proven to be successful, especially if densely functionalised, highly stereoregular polymers are desired. [29][30][31][32][33][34][35][36][37][38][39][40][41][42] Highly stereospecific (co)polymerisation of diazoesters (N 2 CHCOOR) can be achieved in good yields and with high M w in a Rh catalysed process. 30,[43][44][45][46][47][48][49][50][51] This leads to the formation of syndiotactic polymers bearing an ester functionality at every single carbon atom of the polymer main chain.…”

Section: Introductionmentioning

confidence: 99%

A different route to functional polyolefins: olefin–carbene copolymerisation

2013

Self Cite

View full text Add to dashboard Cite

Copolymerisation of carbenes and olefins (ethene), mediated by Rh-based catalyst precursors, is presented as a new, proof-of-concept methodology for the controlled synthesis of functional polymers. The reactions studied show that olefin-carbene polymerisation reactions provide a viable alternative to more traditional olefin polymerization techniques. Rh(III)-catalyst precursors, while active in the homopolymerisation of either olefins or carbenes, proved to be virtually inactive in olefin-carbene copolymerization. Conversely, the use of Rh(I)(cod) catalyst precursors allows the synthesis of high molecular-weight, highly functionalized copolymers. The reactions yield a mixture of copolymers and some carbene homopolymers, which proved to be difficult to separate. Polyethylene was not formed under the applied reaction conditions. The average ethene content in this mixture could be increased up to 11%, although analysis of the mixture revealed that the ethene content in fractions of the copolymer mixture can be as high as 70%. Attempts to increase the ethene content by increasing the ethene pressure unexpectedly led to lower average ethene contents, which is most likely due to changes in the ratio of copolymers vs. carbene homopolymer. This behaviour is most likely a result of the reactivity difference of different active Rh-species formed under the applied reaction conditions. Apparently, higher ethene concentrations slow down the copolymerisation process (mediated by yet unidentified Rh-species) compared to the formation of homopolymers (mediated by different Rh-catalysts; most likely (allyl)Rh(III)-alkyl species), thereby changing the product ratio in favour of the homopolymer. The average ethene content in the copolymer mixture therefore decreases, while the ethene content within the copolymer fraction has likely increased at higher ethene concentrations (but simply less copolymer is formed). The obtained copolymers exhibit a blocky microstructure, with the functional blocks being highly stereoregular. Branching does occur and the functional groups are present in the polymer backbone as well as at the branches. Formation of copolymers was confirmed by Maldi-ToF analysis, which revealed incorporation of several ethene units into the copolymers.

show abstract

“…However, their extremely short lifetimes make their direct detection difficult and impede the development of radical chemistry. Carbenes, from nitrogen-releasing diazo compounds 2 , are the versatile active species in a broad range of reactions, including C-H functionalization 3 4 , carbon-carbon bond formation 5 6 , cyclopropanation 7 8 and polycarbene construction 9 10 11 . Usually, these reactions are carried out with metal catalysts, and the intermediates, generally considered to be metal-carbenes, have attracted much attention over the past decade 12 13 14 15 16 .…”

mentioning

confidence: 99%

Metal-Diazo Radicals of α-Carbonyl Diazomethanes

Xiao

Liu

2016

Sci Rep

View full text Add to dashboard Cite

Metal-diazo radicals of α-carbonyl diazomethanes are new members of the radical family and are precursors to metal-carbene radicals. Herein, using electron paramagnetic resonance spectroscopy with spin-trapping, we detect diazo radicals of α-carbonyl diazomethanes, induced by [Rh Radicals are highly reactive intermediates, long sought because of their importance in understanding reaction mechanisms and finding new reactions 1 . However, their extremely short lifetimes make their direct detection difficult and impede the development of radical chemistry. Carbenes, from nitrogen-releasing diazo compounds 2 , are the versatile active species in a broad range of reactions, including C-H functionalization 3,4 , carbon-carbon bond formation 5,6 , cyclopropanation 7,8 and polycarbene construction 9-11 . Usually, these reactions are carried out with metal catalysts, and the intermediates, generally considered to be metal-carbenes, have attracted much attention over the past decade [12][13][14][15][16] . Recent studies have shown that some metal-carbenes within paramagnetic metal catalysts (such as Co II , Rh II , and Ir II ) are carbon-centered metal-carbene radicals, not closed-shell metal-carbenes [17][18][19] . As such, their metal-diazo-adduct precursors are reasonably postulated to also possess radical character.Because of the vigorous N 2 evolution and high efficiencies of these reactions, few studies have reported such radicals [20][21][22][23] . The EPR signals of some diazo radical cations of diphenyldiazomethanes and their derivatives have been recorded after electrochemical oxidation or irradiation in Freon matrices [24][25][26] . In frozen toluene at 40 K, a carbon-centered Co-carbene radical was detected by EPR spectroscopy, along with several other paramagnetic cobalt species 17 , which complicated the spectral analysis. Diazo radicals may coexist with carbene radicals within reaction systems, and distinguishing them from one another is likewise difficult. Thus, the detection of metal-diazo radicals and their transformations into metal-carbene radicals remain unsolved challenges in diazo chemistry.To overcome these challenges, we employed room-temperature electron paramagnetic resonance (RT-EPR) spectroscopy with a spin-trapping technique 27 , which offers a convenient and powerful way to identify both diazo radicals and carbene radicals and to simultaneously investigate their behaviors. Because of the persistent radical effects of the redox-active metal and nitroxide 1 , the transient radical intermediates can be either directly detected by EPR or captured by radical traps (Fig. 1). In this paper, we report that the use of [RhCl(cod)] 2 (cod = 1,5-cyclooctadiene) allowed the RT-EPR detection of a rather stable dinitrogen radical of α -carbonyl diazomethane as a unique quintet signal. Density function theory (DFT) calculations support the EPR analyses, assigning a significant amount of spin density (97.2%) to the diazo moiety. To our knowledge, this work represents the first unequivocal spectroscopic confi...

show abstract

Carbene insertion into transition metal–carbon bonds: a new tool for catalytic C–C bond formation

Cited by 89 publications

References 87 publications

Stereospecific Carbene Polymerization with Oxygenated Rh(diene) Species

Stereospecific Carbene Polymerization with Oxygenated Rh(diene) Species

A different route to functional polyolefins: olefin–carbene copolymerisation

Metal-Diazo Radicals of α-Carbonyl Diazomethanes

Contact Info

Product

Resources

About