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Innocent and Less‐Innocent Solvent Ligands: A Systematic Investigation of Cationic Iron Chloride/Alcohol Complexes by Electrospray Ionization Mass Spectrometry Complemented by DFT Calculations
Author(s) -
Trage Claudia,
Diefenbach Martin,
Schröder Detlef,
Schwarz Helmut
Publication year - 2006
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.200500718
Subject(s) - chemistry , electrospray ionization , reactivity (psychology) , alcohol , cationic polymerization , coordination sphere , mass spectrometry , ligand (biochemistry) , propanol , methanol , metal , inorganic chemistry , medicinal chemistry , ion , organic chemistry , medicine , biochemistry , alternative medicine , receptor , pathology , chromatography
The influence of anionic and neutral ligands on the reactivity of cationic iron complexes towards methanol, ethanol, and iso‐ and n ‐propanol has been investigated by means of electrospray ionization (ESI) mass spectrometry, and in key questions the experimental results are supported by DFT calculations. The chemical processes taking place when FeCl 2 + is coordinated to a variable number of alcohol molecules were investigated by collision experiments, as well as reactivity and labeling studies. The most abundant cations formed upon ESI of FeCl 3 /ROH mixtures can be described as consisting of a covalently bound FeCl 2 + core, which is stabilized by neutral ROH ligands, for example, FeCl 2 (CH 3 OH) n + . Indications for a hydrogen‐bonding mechanism of ligands in the second coordination sphere are given by the observation of the formally hypercoordinated ion FeCl 2 (CH 3 OH) 5 + and interpretation of kinetic data for n =4. Further, deuterium labeling experiments disclose a number of hidden hydrogen transfers and imply that complexes with n =1 and 2 can exist in two tautomeric forms. Upon change of the alcohol ligand from methanol to ethanol and propanol, additional reaction pathways become accessible, among which metal‐assisted dehydration of the respective alcohols by means of an ion/dipole mechanism is the most important.