Asymmetric Epoxidations with H2O2 on Fe and Mn Aminopyridine Catalysts: Probing the Nature of Active Species by Combined Electron Paramagnetic Resonance and Enantioselectivity Study

ACS Catalysis ◽  
2012 ◽  
Vol 2 (6) ◽  
pp. 1196-1202 ◽  
Author(s):  
Oleg Y. Lyakin ◽  
Roman V. Ottenbacher ◽  
Konstantin P. Bryliakov ◽  
Evgenii P. Talsi
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Active Species ◽  
Paramagnetic Resonance ◽  
Fe And Mn ◽  
Electron Paramagnetic

scholarly journals Spectroscopic Signature and Structure of Active Sites in Ziegler-Natta Polymerization Catalysts revealed by Electron Paramagnetic Resonance

2021 ◽  
Author(s):  
Anton Ashuiev ◽  
Matthieu Humbert ◽  
David Gajan ◽  
Sebastien Norsic ◽  
Jan Blahut ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Ethylene Polymerization ◽  
Active Sites ◽  
Active Species ◽  
Atomic Scale ◽  
Polymerization Catalysts ◽  
Paramagnetic Resonance ◽  
Spectroscopic Signatures ◽  
Electron Paramagnetic ◽  
Ziegler Natta Catalysts

Despite decades of extensive studies, the atomic-scale structure of the active sites in heterogeneous Ziegler-Natta (ZN) catalysts, one of the most important processes of the chemical industry, remains elusive and a matter of debate. In the present work, the structure of “active sites” of ZN catalysts in the absence of ethylene, referred to as “dormant active sites”, is elucidated from magnetic resonance experiments, carried out on samples reacted with increasing amounts of BCl<sub>3</sub> so as to enhance the concentration of active sites and observe clear spectroscopic signatures. Using EPR and NMR spectroscopies, in particular 2D HYSCORE experiments complemented by DFT calculations, we show that the activated ZN catalysts contain bimetallic alkyl-Ti(III),Al species whose amount is directly linked to the polymerization activity of MgCl<sub>2</sub>-supported Ziegler-Natta catalysts. This connects those spectroscopic signatures to the active species formed in the presence of ethylene, and enables us propose an ethylene polymerization mechanism on the observed bimetallic alkyl-Ti(III),Al species based on DFT computations<br>

The electron paramagnetic resonance of polyradicals

1999 ◽  
Vol 96 (9/10) ◽  
pp. 1551-1558 ◽  
Author(s):  
L. Catala ◽  
P. Turek
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

ELECTRON PARAMAGNETIC RESONANCE STUDIES OF PHASE TRANSITIONS IN KCN

1976 ◽  
Vol 37 (C7) ◽  
pp. C7-241-C7-246 ◽  
Author(s):  
J.P. VON DER WEID ◽  
L.C. SCAVARDA DO CARMO ◽  
R. R. DO SANTOS ◽  
B. KOILLER ◽  
S. COSTA RIBEIRO ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Phase Transitions ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

Electron paramagnetic resonance in silicon and germanium

1964 ◽  
Vol 83 (7) ◽  
pp. 433-502 ◽  
Author(s):  
L.D. Bogomolova ◽  
V.N. Lazukin ◽  
I.V. Chepeleva
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Paramagnetic Resonance ◽  
Silicon And Germanium ◽  
Electron Paramagnetic
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