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Title: Anion control of tautomeric equilibria: Fe–H vs. N–H influenced by NH⋯F hydrogen bonding

Journal Article · · Chemical Science
DOI:https://doi.org/10.1039/C8SC04239J· OSTI ID:1483140
 [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, USA
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Counterions can play an active role in chemical reactivity, modulating reaction pathways, energetics and selectivity. We investigated the tautomeric equilibrium resulting from protonation of Fe(PEtNMePEt)(CO)3 (PEtNMePEt = (Et2PCH2)2NMe) at Fe or N. Protonation of Fe(PEtNMePEt)(CO)3 by [(Et2O)2H]+[B(C6F5)4]- occurs at the metal to give the iron hydride [Fe(PEtNMePEt)(CO)3H]+[B(C6F5)4]-. In contrast, treatment with HBF4·OEt2 gives protonation at the iron and at the pendant amine. Both the FeH and NH tautomers were characterized by single crystal X-ray diffraction. Addition of excess BF4- to the equilibrium mixture leads to the NH tautomer being exclusively observed, due to NH•••F hydrogen bonding. A quantum chemical analysis of the bonding properties of these systems provided a quantification of hydrogen bonding of the NH to BF4- and to OTf-. Treatment of Fe(PEtNMePEt)(CO)3 with excess HOTf gives a dicationic complex where both the iron and nitrogen are protonated. Isomerization of the dicationic complex was studied by NOESY NMR spectroscopy.

Research Organization:
Energy Frontier Research Centers (EFRC) (United States). Center for Molecular Electrocatalysis (CME); Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
AC05-76RL01830
OSTI ID:
1483140
Alternate ID(s):
OSTI ID: 1501649
Report Number(s):
PNNL-SA-135803; CSHCBM
Journal Information:
Chemical Science, Journal Name: Chemical Science Vol. 10 Journal Issue: 5; ISSN 2041-6520
Publisher:
Royal Society of Chemistry (RSC)Copyright Statement
Country of Publication:
United Kingdom
Language:
English
Citation Metrics:
Cited by: 11 works
Citation information provided by
Web of Science

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Cited By (2)

Evaluation of attractive interactions in the second coordination sphere of iron complexes containing pendant amines journal January 2019
Electron acceptors promote proton–hydride tautomerism in low valent rhenium β-diketiminates journal January 2020

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
hydrogen bonding