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Updated: Sep 11, 2025

Line Shape Analysis of Dynamic NMR Spectra for Characterizing Coordination Sphere Rearrangements at a Chiral Rhenium Polyhydride Complex
Published on: July 27, 2022
Dynamic processes of the first NHC-substituted rhenium heptahydrides [ReH7(NHC)2]
G Grieco1, A Pierini2, M Pierini3
1University of Zurich, Department of Chemistry, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland. pgag.2021@gmail.com.
None:
In this paper are presented possible geometries and fluxional mechanisms of three [ReH7(NHC)2] complexes (NHC = IMes (1) (1,3-bis(2,4,6-trimethyl phenyl) imidazol-2-ylidene), IMesCl2 (2) (4,5-dichloro-1,3-dihydro-1,3-bis(2,4,6-trimethylphenyl)-2H-imidazol-2-ylidene), BIMes (3) (1,3-bis(2,4,6-trimethylphenyl)-benzo imidazole ylidene)). Using DFT calculations, plausible fluxional processes were proposed, and a new process named "η2-quadratic twist" has been identified. For 2 the intermediate complex [Re(H)5(η2-H2)(IMesCl2)2] proved to be more energetically accessible at RT than those of the complexes 1 ([Re(H)5(η2-H2)(IMes)2]) and 3 ([Re(H)5(η2-H2)(BIMes)2]). Two different fluxional mechanisms have been proposed: the first one for 1 and 3, and the second one for 2. The mechanism for complex 2 implies the C-H activation of the hydrogens of the o-CH3 group of the IMesCl2 ligands.
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