Solid State lonics 63-65 ( 1993 ) 346-350 North-Holland SOLID STATE IONICS Structure and thermochemical reactivity of Cu (NH3) 2CO3 M. Maciejewski, A. Baiker, H. Viebrock Department of Chemical Engineeringand Industrial Chemistry, Swiss FederalInstitute of Technology, ETH-Zentrum, CH-8092 Zurich, Switzerland U. Sazama, P.-M. Wilde and A. Relier Institutefor Inorganic and Applied Chemistry, Universityof Hamburg, Martin-Luther-King-Platz6, D-2000 Hamburg 13, Germany The structure and atmosphere-dependent thermochemical reactivity of diammine copper carbonate, Cu (NH 3)2CO3 has been investigated by means of combined thermoanalytical/mass spectrometric measurements, single crystal and powder X-ray diffrac- tion studies as well as scanning electron microscopy. It could be shown that in reducing atmosphere a series of different organic volatile species as well as Cu ° are formed. This observation is explained in terms of the structural vicinity of potential volatile agents in the parent material, i.e. NH3 and CO2, as well as the in situ formation of catalytically active solid products during the thermochemical degradation. 1. Introduction During thermal decompositions of solids, simul- taneous and sequential heterogeneous and homoge- neous processes occur. Whereas most often the solid products are of paramount interest, the volatile products are only rarely specified. This may be ex- plained by the importance of generating solids with specific textural, chemical or physical properties via controlled decomposition of precursor compounds. The influence of the gas atmosphere under which such reactions are performed is decisive for the for- mation of solid and volatile products. Thus a de- tailed analysis of the composition of the evolved vol- atile compounds gives insights into the mechanism of the over-all process, in particular on the possibil- ity of in situ formation of catalytically active species. It has been shown for the decomposition of mixed alkaline earth/transition metal carbonates in hydro- gen [ 1,2 ] as well as for transition metal acetates in hydrogen [3], that the composition of the evolved volatile species can only be explained by in situ cat- alytic activity of solid products. This study focusses on the thermochemical reac- tivity of the title compound, the solid complex Cu(NH3)2CO 3. Whereas the structure determina- tion [4] as well as thermogravimetric measurements of the decomposition in air have been published [5], the influence of the atmosphere on the mechanism of the degradation as well as on the corresponding composition of the volatile products has not been in- vestigated yet. Moreover, the structural features of the title compound are such, that on an atomic level carbonate anions and ammine ligands are positioned in the first coordination sphere of the copper metal cation. If the mechanism of the decomposition of the title compound leads to the formation of a catalyt- ically active metal species, the secondary generation of non-expected volatile products by this catalyti- cally active site should be observed during the over- all process. In turn the main question could be an- swered whether during the decomposition an in situ formation of catalytically active copper species yields comprehensive information on the spectrum of vol- atile species, which can be obtained in dependence of the experimental conditions, above all in depen- dence of the ambient atmosphere. Finally, the ques- tion should be answered whether the formation of -C-H-, -C-C- or -C-N- bonds may occur under the given preconditions. 0167-2738/93/$ 06.00 © 1993 Elsevier Science Publishers B.V. All rights reserved.