Breternitz, Joachim

Gregory, Duncan H.

Hoang, Tuan K.A.

English

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n       Breternitz, J., Hoang, T. K.A., and Gregory, D. H. (2013) Unusual structural phenomena in the reaction of copper and nickel dihalides with NH3(g) at ambient conditions. Acta Crystallographica. Section A: Foundations of Crystallography, A69 . s580. ISSN 0108-7673   Copyright © 2013 The Authors     http://eprints.gla.ac.uk/97410/       Deposited on:  24 September 2014                   Enlighten – Research publications by members of the University of Glasgow http://eprints.gla.ac.uk Page s580  28th European Crystallographic Meeting, ECM 28, UK, 2013 Acta Cryst. (2013). A69, s580[MS28-P03] Unusual Structural Phenomena in the Reaction of Copper and Nickel Dihalides with NH3(g) at Ambient Conditions. Joachim Breternitz,a Tuan K. A. Hoang,a Duncan H. Gregory*a a WestCHEM, School of Chemistry, University of Glasgow, University Avenue, Glasgow G12 8QQ, Scotland, UK. Duncan.Gregory@glasgow.ac.uk E-mail: joachim@chem.gla.ac.uk While many solid state reactions take place slowly at high temperatures (and in some cases high pressures), the reversible ammoniation – deammoniation of many metal halides is a process which occurs at near-ambient conditions. Given the potential of ammonia as a “clean” fuel, the facile NH3 uptake and release in metal halides advocates the use of these compounds as solid state ammonia storage materials.[1,2] We present here work concerning the direct reaction between NiX2 (X = Cl, Br, I) or CuX2(X = Cl, Br) and gaseous ammonia at ambient temperature and pressure. The reaction of NiX2 with NH3(g) produces the stoichiometric product [Ni(NH3)6]X2 within one hour as nano-sized crystallites. Despite the ease of the ammonia sorption, it is noteworthy that the reaction is by no means topotactic. In fact, it demands a complete structural rearrangement from layered NiX2 (CdCl2 type, R-3m; e.g. with Ni–X distances of 243 pm for X = Cl)[3] to structures comprising isolated complex cations [Ni(NH3)6]2+ bound to halide anions (e.g. with Ni–X distances of 436 pm for X = Cl). Furthermore, NH3 can be removed from [Ni(NH3)6]X2 (cubic, Fm-3m) by simple thermal activation, which occurs in a two step process with NiX2·2NH3 (Cmmm for X = Cl, Br, I or Pbam for X = Br, I)[4] as an intermediate phase and finally yielding the original starting material, NiX2. This reversible ammonia sorption coupled with a high gravimetric capacity (44 wt.-% NH3 for X = Cl) places nickel halides among the most promising ammonia storage materials for use in mobile fuel cell applications. The case for copper ammines is somewhat contrasting in that the structure of copper complexes is mediated by the Jahn-Teller effect. As a result the hexammine exits as a (non-standard) F4/mmm structure with an elongated c-axis compared to the cubic Ni(NH3)6X2 structure.[5] The reaction of NH3 with CuX2(X = Cl, Br) to form the hexammines occurs readily at ambient temperature. Rietveld refinement against XRD data for the chloride revealed an ammonia deficit on the elongated axial sites leading to a composition of [Cu(NH3)5.22(4)]Cl2. This ammonia deficit suggests that these ammines should be defined as [CuL4L(2–x)]X2 complexes. The authors would like to thank EADS Innovation Works for funding. [1] Sørensen, R. Z., Hummelshøj, J. S., Klerke, A., Reves, J. B., Vegge, T., Nørskov, J. K. & Christensen, C. H. (2008). J. Am. Chem. Soc. 130, 8660–8668. [2] Reardon, H., Hanlon, J. M., Grant, M., Fullbrook, I. & Gregory, D. H. (2012). Crystals 2, 193–212. [3] Ferrari, A., Braibanti, A. & Bigliardi, G. (1963). Acta Cryst. 16, 846–847. [4] Leineweber, A. & Jacobs, H. (2000). J. Solid State Chem. 152, 381–387. [5] Distler, T. M. & Vaughan, P. A. (1967). Inorg. Chem. 6, 126–129. Keywords: energy materials, transition-metal complex

Unusual structural phenomena 

in the reaction of copper and nickel dihalides with NH<sub>3(g)</sub> at ambient conditions

Enlighten: Publications

n 
 
 
 
 
 
 
Breternitz, J., Hoang, T. K.A., and Gregory, D. H. (2013) Unusual 
structural phenomena in the reaction of copper and nickel dihalides with 
NH3(g) at ambient conditions. Acta Crystallographica. Section A: 
Foundations of Crystallography, A69 . s580. ISSN 0108-7673 
 
 
Copyright © 2013 The Authors 
  
 
 
http://eprints.gla.ac.uk/97410/  
 
 
 
 
 
Deposited on:  24 September 2014 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Enlighten – Research publications by members of the University of Glasgow 
http://eprints.gla.ac.uk 
Page s580  28th European Crystallographic Meeting, ECM 28, UK, 2013 Acta Cryst. (2013). A69, s580
[MS28-P03] Unusual Structural Phenomena 
in the Reaction of Copper and Nickel Dihalides 
with NH
3(g)
 at Ambient Conditions. 
Joachim Breternitz,
a 
Tuan K. A. Hoang,
a 
Duncan 
H. Gregory*
a 
a 
WestCHEM, School of Chemistry, University of 
Glasgow, University Avenue, Glasgow G12 8QQ, 
Scotland, UK. Duncan.Gregory@glasgow.ac.uk 
E-mail: joachim@chem.gla.ac.uk 
While many solid state reactions take place 
slowly at high temperatures (and in some cases 
high pressures), the reversible ammoniation 
– deammoniation of many metal halides is a 
process which occurs at near-ambient conditions. 
Given the potential of ammonia as a “clean” 
fuel, the facile NH3 uptake and release in metal 
halides advocates the use of these compounds as 
solid state ammonia storage materials.[1,2] We 
present here work concerning the direct reaction 
between NiX2 (X = Cl, Br, I) or CuX2(X = Cl, Br) 
and gaseous ammonia at ambient temperature 
and pressure. The reaction of NiX2 with NH3(g) 
produces the stoichiometric product [Ni(NH3)6]
X2 within one hour as nano-sized crystallites. 
Despite the ease of the ammonia sorption, it 
is noteworthy that the reaction is by no means 
topotactic. In fact, it demands a complete structural 
rearrangement from layered NiX2 (CdCl2 type, 
R-3m; e.g. with Ni–X distances of 243 pm for 
X = Cl)[3] to structures comprising isolated 
complex cations [Ni(NH3)6]
2+ 
bound to halide 
anions (e.g. with Ni–X distances of 436 pm for 
X = Cl). Furthermore, NH3 can be removed from 
[Ni(NH3)6]X2 (cubic, Fm-3m) by simple thermal 
activation, which occurs in a two step process with 
NiX2·2NH3 (Cmmm for X = Cl, Br, I or Pbam for 
X = Br, I)[4] as an intermediate phase and finally 
yielding the original starting material, NiX2. This 
reversible ammonia sorption coupled with a high 
gravimetric capacity (44 wt.-% NH3 for X = Cl) 
places nickel halides among the most promising 
ammonia storage materials for use in mobile fuel 
cell applications. The case for copper ammines 
is somewhat contrasting in that the structure of 
copper complexes is mediated by the Jahn-Teller 
effect. As a result the hexammine exits as a (non-
standard) F4/mmm structure with an elongated 
c-axis compared to the cubic Ni(NH3)6X2 
structure.[5] The reaction of NH3 with CuX2(X = 
Cl, Br) to form the hexammines occurs readily at 
ambient temperature. Rietveld refinement against 
XRD data for the chloride revealed an ammonia 
deficit on the elongated axial sites leading to a 
composition of [Cu(NH3)5.22(4)]Cl2. This ammonia 
deficit suggests that these ammines should be 
defined as [CuL4L(2–x)]X2 complexes. 
The authors would like to thank EADS Innovation 
Works for funding. 
[1] Sørensen, R. Z., Hummelshøj, J. S., Klerke, 
A., Reves, J. B., Vegge, T., Nørskov, J. K. & 
Christensen, C. H. (2008). J. Am. Chem. Soc. 
130, 8660–8668. 
[2] Reardon, H., Hanlon, J. M., Grant, M., 
Fullbrook, I. & Gregory, D. H. (2012). Crystals 
2, 193–212. 
[3] Ferrari, A., Braibanti, A. & Bigliardi, G. 
(1963). Acta Cryst. 16, 846–847. 
[4] Leineweber, A. & Jacobs, H. (2000). J. Solid 
State Chem. 152, 381–387. 
[5] Distler, T. M. & Vaughan, P. A. (1967). Inorg. 
Chem. 6, 126–129. 
Keywords: energy materials, transition-metal 
complex


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Unusual structural phenomena in the reaction of copper and nickel dihalides with NH<sub>3(g)</sub> at ambient conditions

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