On the solvation of metal ions in liquid ammonia: a molecular simulation study of M(NH2)x(NH3)ycomplexes as a function of pH
Open Access
- 24 November 2017
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in RSC Advances
- Vol. 7 (85), 54063-54067
- https://doi.org/10.1039/c7ra11462a
Abstract
The solvation of mono-, di- and trivalent metal ions in liquid ammonia is characterized from molecular simulations. A central focus of the analyses is given by metal ion acidity within the respective solvent complexes. For this purpose, a recently developed model for estimating the pK of the auto-protolysis reaction 2NH3 → NH4 + + NH2 − is transferred to assessing the ‘local’ pK of ammonia molecules coordinating a metal ion. On this basis, we identify MI/II(NH3)n +/++ complexes (M = Na+, K+, Mg2+ with n = 6 and M = Ca2+ with n = 8, respectively) as predominant species unless extremely ammono-basic conditions are imposed. On the other hand, the trivalent Al3+ and Ga3+ species were found to favor [Al(NH2)3(NH3)2]0 and [Ga(NH2)4]− complexes, respectively. The negatively charged complexes dominate over a wide range of pH for gallium ion solvation in ammonia, whilst [Al(NH2)4(NH3)2]− complexes require moderately ammono-basic solutions.Funding Information
- Deutsche Forschungsgemeinschaft (EXC 315)
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