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Crystals 2012, 2(2), 193-212; doi:10.3390/cryst2020193
Article

Ammonia Uptake and Release in the MnX2–NH3 (X = Cl, Br) Systems and Structure of the Mn(NH3)nX2 (n = 6, 2) Ammines

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WestCHEM, School of Chemistry, University of Glasgow, Joseph Black Building, Glasgow G12 8QQ, UK
* Author to whom correspondence should be addressed.
Received: 21 February 2012 / Revised: 18 March 2012 / Accepted: 30 March 2012 / Published: 10 April 2012
(This article belongs to the Special Issue Hydrogen Storage Alloys)
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Abstract

Hexa-ammine complexes, Mn(NH3)6X2 (X = Cl, Br), have been synthesized by ammoniation of the corresponding transition metal halide and characterized by Powder X-ray diffraction (PXRD) and Raman spectroscopy. The hexa-ammine complexes are isostructural (Cubic, Fm-3m, Z = 4; a = 10.2742(6) Å and 10.527(1) Å for X = Cl, Br respectively). Temperature programmed desorption (TPD) demonstrated that ammonia release from Mn(NH3)6X2 complexes occurred in three stages corresponding to the release of 4, 1 and 1 NH3 equivalents respectively. The chloride and bromide both exhibit a deammoniation onset temperature below 323 K. The di-ammoniates from the first desorption step were isolated during TPD measurements and their crystal structures determined by Rietveld refinement against PXRD data (X = Cl: orthorhombic Cmmm, a = 8.1991(9) Å, b = 8.2498(7) Å, c = 3.8212(4) Å, Z = 2; X = Br: orthorhombic Pbam, a = 6.0109(5) Å, b = 12.022(1) Å, c = 4.0230(2) Å, Z = 2).
Keywords: manganese; ammines; chloride; bromide; structure; Raman; ammonia storage; hydrogen storage manganese; ammines; chloride; bromide; structure; Raman; ammonia storage; hydrogen storage
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Reardon, H.; Hanlon, J.M.; Grant, M.; Fullbrook, I.; Gregory, D.H. Ammonia Uptake and Release in the MnX2–NH3 (X = Cl, Br) Systems and Structure of the Mn(NH3)nX2 (n = 6, 2) Ammines. Crystals 2012, 2, 193-212.

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