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

Geoffrey M. Chambers, Samantha I. Johnson, Simone Raugei, R. Morris Bullock

Research output: Contribution to journalArticle

2 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)1410-1418
Number of pages9
JournalChemical Science
Volume10
Issue number5
DOIs
Publication statusPublished - Jan 1 2019

ASJC Scopus subject areas

  • Chemistry(all)

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