Is Electronegativity a Useful Descriptor for the Pseudo-Alkali Metal NH4?
Article first published online: 19 SEP 2011
Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Chemistry - A European Journal
Volume 17, Issue 47, pages 13197–13205, November 18, 2011
How to Cite
Whiteside, A., Xantheas, S. S. and Gutowski, M. (2011), Is Electronegativity a Useful Descriptor for the Pseudo-Alkali Metal NH4?. Chem. Eur. J., 17: 13197–13205. doi: 10.1002/chem.201101949
- Issue published online: 14 NOV 2011
- Article first published online: 19 SEP 2011
- Manuscript Received: 23 JUN 2011
- Department of Energy
- alkali metals;
- computational chemistry;
- ion pairs
Molecular ions in the form of “pseudo-atoms” are common structural motifs in chemistry, with properties that are transferrable between different compounds. We have determined one such property—the electronegativity—for the “pseudo-alkali metal” ammonium (NH4), and evaluated its reliability as a descriptor versus the electronegativities of the alkali metals. The computed properties of ammonium’s binary complexes with astatine and of selected borohydrides confirm the similarity of NH4 to the alkali metal atoms, although the electronegativity of NH4 is relatively large in comparison to its cationic radius. We have paid particular attention to the molecular properties of ammonium (angular anisotropy, geometric relaxation and reactivity), which can cause deviations from the behaviour expected of a conceptual “true alkali metal” with this electronegativity. These deviations allow for the discrimination of effects associated with the molecular nature of NH4.