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

Abstract

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.

Authors:
 [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. Center for Molecular Electrocatalysis, Pacific Northwest National Laboratory, Richland, USA
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Center for Molecular Electrocatalysis (CME); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
OSTI Identifier:
1483140
Alternate Identifier(s):
OSTI ID: 1501649
Report Number(s):
PNNL-SA-135803
Journal ID: ISSN 2041-6520; CSHCBM
Grant/Contract Number:  
AC05-76RL01830
Resource Type:
Published Article
Journal Name:
Chemical Science
Additional Journal Information:
Journal Name: Chemical Science Journal Volume: 10 Journal Issue: 5; Journal ID: ISSN 2041-6520
Publisher:
Royal Society of Chemistry (RSC)
Country of Publication:
United Kingdom
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; hydrogen bonding

Citation Formats

Chambers, Geoffrey M., Johnson, Samantha I., Raugei, Simone, and Bullock, R. Morris. Anion control of tautomeric equilibria: Fe–H vs. N–H influenced by NH⋯F hydrogen bonding. United Kingdom: N. p., 2019. Web. doi:10.1039/C8SC04239J.
Chambers, Geoffrey M., Johnson, Samantha I., Raugei, Simone, & Bullock, R. Morris. Anion control of tautomeric equilibria: Fe–H vs. N–H influenced by NH⋯F hydrogen bonding. United Kingdom. doi:10.1039/C8SC04239J.
Chambers, Geoffrey M., Johnson, Samantha I., Raugei, Simone, and Bullock, R. Morris. Wed . "Anion control of tautomeric equilibria: Fe–H vs. N–H influenced by NH⋯F hydrogen bonding". United Kingdom. doi:10.1039/C8SC04239J.
@article{osti_1483140,
title = {Anion control of tautomeric equilibria: Fe–H vs. N–H influenced by NH⋯F hydrogen bonding},
author = {Chambers, Geoffrey M. and Johnson, Samantha I. and Raugei, Simone and Bullock, R. Morris},
abstractNote = {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.},
doi = {10.1039/C8SC04239J},
journal = {Chemical Science},
number = 5,
volume = 10,
place = {United Kingdom},
year = {2019},
month = {1}
}

Journal Article:
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DOI: 10.1039/C8SC04239J

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