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Coordination of Iron( III ) Cations to β‐Keto Esters as Studied by Electrospray Mass Spectrometry: Implications for Iron‐Catalyzed Michael Addition Reactions
Author(s) -
Trage Claudia,
Schröder Detlef,
Schwarz Helmut
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400715
Subject(s) - chemistry , counterion , electrospray ionization , catalysis , mass spectrometry , mass spectrum , metal , electrospray mass spectrometry , electrospray , inorganic chemistry , medicinal chemistry , ion , organic chemistry , chromatography
Solutions of Fe III salts and β‐keto esters have been investigated by means of electrospray ionization mass spectrometry. The complexes formed in such solutions have been considered previously as active intermediates in Fe III ‐catalyzed Michael additions. By using different Fe III salts with a set of β‐keto esters, cation and anion mass spectra were analyzed and the effects of ester concentration, the role of the counterion, and the structure of the ester employed are discussed. Depending on the basicity of the ester, an increase of its concentration may lead to a decrease in the concentration of iron complexes observed in the mass spectra. Counterions with strong binding affinities to iron are found to capture the metal as ferrates, thereby removing the metal from the catalytic cycle.