Identification of a Two‐Coordinate Iron(I)–Oxalate Complex
Martin Mayer, Nina Vankova, Ferdinand Stolz, Bernd Abel, Thomas Heine, Knut R. Asmis
Abstract
Abstract Exotic oxidation states of the first‐row transition metals have recently attracted much interest. In order to investigate the oxidation states of a series of iron–oxalate complexes, an aqueous solution of iron(III) nitrate and oxalic acid was studied by infrared free liquid matrix‐assisted laser desorption/ionization as well as ionspray mass spectrometry. Here, we show that iron is not only detected in its common oxidation states +II and +III, but also in its unusual oxidation state +I, detectable in both positive‐ion and in negative‐ion modes, respectively. Vibrational spectra of the gas phase anionic iron oxalate complexes [Fe III (C 2 O 4 ) 2 ] − , [Fe II (C 2 O 4 )CO 2 ] − , and [Fe I (C 2 O 4 )] − were measured by means of infrared photodissociation spectroscopy and their structures were assigned by comparison to anharmonic vibrational spectra based on second‐order perturbation theory.