Dynamic Motion in [Hfe(CO)₄]- Ions as Observed by Mössbauer Spectroscopy - Evidence for Hydride “tunneling”
The iron atom is moved by up to 0.34 Å from its original position in the anion [HFe(CO4)−] when the temperature is increased. This is suggested by the results of Mössbauer spectroscopy at temperatures from 78 to 280 K on a series of ammonium salts with this anion. the displacement is induced by a movement of the ligands and is in accord with a rapid change of position (“tunneling”) of the hydrido ligands, which makes the four carbonyl ligands equivalent. the Gibbs free energy of activation for the tunneling, determined from the temperature dependence of the displacement of the iron atom, is 29.2 kJ mol−1 for the Et4N+ salt and only 9.7 kJ mol−1 for the Me4N+ salt.
G. J. Long et al., "Dynamic Motion in [Hfe(CO)₄]- Ions as Observed by Mössbauer Spectroscopy - Evidence for Hydride “tunneling”," Angewandte Chemie International Edition, Wiley-VCH Verlag, Jan 1992.
The definitive version is available at http://dx.doi.org/10.1002/anie.199208841
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© 1992 Wiley-VCH Verlag, All rights reserved.