ChemInform Abstract: ESR Study on the σ‐ and π‐Radical Cations Formed by One‐Electron Oxidation of Phenyldiazomethanes.

Ishiguro, Katsuya; Sawaki, Yasuhiko; Izuoka, Akira; Sugawara, Tadashi; Iwamura, Hiizu

doi:10.1002/chin.198734138

ChemInform

1987

DOI: 10.1002/chin.198734138

|View full text |Cite

ChemInform Abstract: ESR Study on the σ‐ and π‐Radical Cations Formed by One‐Electron Oxidation of Phenyldiazomethanes.

Katsuya Ishiguro

Yasuhiko Sawaki

Akira Izuoka

et al.

Abstract: 138ChemInform Abstract The radical cations from (I) and (II) obtained during electrochemical oxidation at low temp. seem to have a "σ-radical" structure, in which an unpaired electron is localized on two nitrogens. The half-life of (I) (R: -Ph) is about 10s at -33 rc C and 90s at -83 rc C. The radical cations derived from (III), however, have clearly a "π-radical" structure, the spin density being delocalized on both diazo and phenyl groups. These radical cations are relatively stable with half-lives of ca. 10… Show more

Help me understand this report

Search citation statements

Order By: Relevance

Paper Sections

Select...

Citation Types

Supporting

Mentioning

Contrasting

Year Published

2016

Publication Types

Select...

Article1

Relationship

Self Cite0

Independent1

Authors

Journals

Cited by 1 publication

(1 citation statement)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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.…”

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

mentioning

confidence: 99%

Metal-Diazo Radicals of α-Carbonyl Diazomethanes

Xiao

Liu

2016

Sci Rep

View full text Add to dashboard Cite

show abstract

scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.

Contact Info

customersupport@researchsolutions.com

10624 S. Eastern Ave., Ste. A-614

Henderson, NV 89052, USA

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

Blog Terms and Conditions API Terms Privacy Policy Contact Cookie Preferences Do Not Sell or Share My Personal Information

Made with 💙 for researchers

Part of the Research Solutions Family.

ChemInform Abstract: ESR Study on the σ‐ and π‐Radical Cations Formed by One‐Electron Oxidation of Phenyldiazomethanes.

Cited by 1 publication

References 1 publication

Metal-Diazo Radicals of α-Carbonyl Diazomethanes

Metal-Diazo Radicals of α-Carbonyl Diazomethanes

Contact Info

Product

Resources

About