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A Series of Diamagnetic Pyridine Monoimine Rhenium Complexes with Different Degrees of Metal-to-Ligand Charge Transfer: Correlating ^(13)C NMR Chemical Shifts with Bond Lengths in Redox-Active Ligands

Sieh, Daniel and Kubiak, Clifford P. (2016) A Series of Diamagnetic Pyridine Monoimine Rhenium Complexes with Different Degrees of Metal-to-Ligand Charge Transfer: Correlating ^(13)C NMR Chemical Shifts with Bond Lengths in Redox-Active Ligands. Chemistry: a European Journal, 22 (30). pp. 10638-10650. ISSN 0947-6539. https://resolver.caltech.edu/CaltechAUTHORS:20160627-120321347

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Abstract

A set of pyridine monoimine (PMI) rhenium(I) tricarbonyl chlorido complexes with substituents of different steric and electronic properties was synthesized and fully characterized. Spectroscopic (NMR and IR) and single-crystal X-ray diffraction analyses of these complexes showed that the redox-active PMI ligands are neutral and that the overall electronic structure is little affected by the choices of the substituent at the ligand backbone. One- and two-electron reduction products were prepared from selected starting compounds and could also be characterized by multiple spectroscopic methods and X-ray diffraction. The final product of a one-electron reduction in THF is a diamagnetic metal–metal-bonded dimer after loss of the chlorido ligand. Bond lengths in and NMR chemical shifts of the PMI ligand backbone indicate partial electron transfer to the ligand. Two-electron reduction in THF also leads to the loss of the chlorido ligand and a pentacoordinate complex is obtained. The comparison with reported bond lengths and ^(13)C NMR chemical shifts of doubly reduced free pyridine monoaldimine ligands indicates that both redox equivalents in the doubly reduced rhenium complex investigated here are located in the PMI ligand. With diamagnetic complexes varying over three formal reduction stages at the PMI ligand we were, for the first time, able to establish correlations of the ^(13)C NMR chemical shifts with the relevant bond lengths in redox-active ligands over a full redox series.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1002/chem.201600679DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/chem.201600679/abstractPublisherArticle
ORCID:
AuthorORCID
Kubiak, Clifford P.0000-0003-2186-488X
Additional Information:© 2016 Wiley-VCH Verlag GmbH & Co. Received: February 14, 2016. Version of Record online: 20 Jun 2016. This material is based upon work performed by the Joint Center for Artificial Photosynthesis, a DOE Energy Innovation Hub, supported through the Office of Science of the U.S. Department of Energy under Award Number DE-SC0004993. Michael Takase, Lawrence M. Henling and David G. VanderVelde are thanked for their invaluable work in the X-ray (M.T. and L.M.H.) and NMR (D.G.V.V) facilities at Caltech and a lot of helpful discussions. The authors are indebted to Natascha Junker, Bernhard E. C. Bugenhagen, and especially Prof. Peter Burger for help with the DFT calculations and generous computation time on the IAAC cluster at the University of Hamburg.
Group:JCAP
Funders:
Funding AgencyGrant Number
Department of Energy (DOE)DE-SC0004993
Subject Keywords:alpha diimines; NMR spectroscopy; redox-active ligands; rhenium; X-ray crystallography
Issue or Number:30
Record Number:CaltechAUTHORS:20160627-120321347
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20160627-120321347
Official Citation:D. Sieh, C. P. Kubiak, Chem. Eur. J. 2016, 22, 10638.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:68689
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:28 Jun 2016 16:15
Last Modified:09 Mar 2020 13:18

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