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Knecht-Chemrxiv-Indirect Detection of Short-lived Hydride Intermediates of Iridium N-Heterocyclic Carbene Complexes via Chemical Exchange Saturation Transfer (CEST) Spectroscopy.pdf (2.79 MB)
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Indirect Detection of Short-lived Hydride Intermediates of Iridium N-Heterocyclic Carbene Complexes via Chemical Exchange Saturation Transfer (CEST) Spectroscopy

preprint
submitted on 23.04.2019 and posted on 24.04.2019 by Stephan Knecht,, Sara Hadjiali, Danila Barskiy, Alexander Pines, Grit Sauer, Alexey S Kiryutin, Konstantin Ivanov, Alexandra V. Yurkovskaya, Gerd Buntkowsky
For the first time chemical-exchange saturation transfer (CEST) 1H NMR is utilized for the study of short-lived hydride intermediates in the catalytic cycle of the Iridium-based organometallic complex [Ir(IMes)(Py)3(H)2]Cl, which are often not observable by other NMR techniques, since they are low concentrated, and undergo reversible ligand exchange with the main complex. The intermediate complexes [Ir(Cl)(IMes)(Py)2(H)2] and [Ir(CD3OD)(IMes) (Py)2(H)2] are detected, assigned and characterized in situ and at room temperature in solution. Understanding the effects on the spin dynamics induced by these complexes is necessary for enhancing the performance of the nuclear spin hyperpolarization technique SABRE (Signal Amplification By Reversible Exchange). By eliminating [Ir(Cl)(IMes)(Py)2(H)2] and manipulating the spin-system by RF-irradiation, we were able to increase the nuclear spin singlet lifetime of the two protons in the main hydride complex by more than an order of magnitude, from 2.2±0.1 s to 27.2±1.2 s. The presented CEST NMR approach has a large application potential for studying short-lived hydride intermediates in catalytic reactions.

Funding

DFG-RSF 19-43-04116

DFG Bu-911-29-1

History

Email Address of Submitting Author

gerd.buntkowsky@chemie.tu-darmstadt.de

Institution

Technische Universitaet Darmstadt

Country

Germany

ORCID For Submitting Author

0000-0003-1304-9762

Declaration of Conflict of Interest

No conflict of interests

Version Notes

Version 2019/04/23

Licence

Exports