Topochemical anion metathesis routes to the Zr2N2S phases and the Na2S and ACl derivatives (A = Na, K, Rb)

Stoltz, C. ; Ramesha, K. ; Sirchio, S. A. ; Gonen, Z. S. ; Eichhorn, B. W. ; Salamanca-Riba, L. ; Gopalakrishnan, J. (2003) Topochemical anion metathesis routes to the Zr2N2S phases and the Na2S and ACl derivatives (A = Na, K, Rb) Journal of the American Chemical Society, 125 (14). pp. 4285-4292. ISSN 0002-7863

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Official URL: http://pubs.acs.org/doi/abs/10.1021/ja0210650

Related URL: http://dx.doi.org/10.1021/ja0210650

Abstract

Anion metathesis reactions between ZrNCl and A2S (A = Na, K, Rb) in the solid state follow three different pathways depending on reaction temperature and reactant stoichiometry: (1) the reaction of ZrNCl with A2S in the 2:1 stoichiometry at 800°C/72 h/in vacuo yields α-Zr2N2S with the expected layered structure of La2O2S. Above 850 °C, α-Zr2N2S (P3m1; a = 3.605(1) Å, c = 6.421(3) Å) neatly transforms to β-Zr2N2S (P63/mmc: a = 3.602(1) Å, c = 12.817(1) Å). The structures of the α- and β-forms are related by an a/2 shift of successive Zr2N2 layers. (2) The same reaction at low temperatures (300-400 °C) yields ACl intercalated phases of the formula AxZr2N2SClx (0 < x < 0.15), where alkali ions are inserted between the S/Cl···S/Cl van der Waals gap of a ZrNCl-type structure. The S and Cl ions are disordered and the c lattice parameters are alkali dependent (R3m, a ~3.6 Å, c ~28.4 (Na), 28.9 (K), and 30.5 Å (Rb). AxZr2N2SClx phases are hygroscopic and reversibly absorb water to give monohydrates. (3) Reaction of ZrNCl with excess A2S at 400-1000°C gives A2S intercalated phases of the formula A2xZr2N2S1+x (0 < x < 0.5), where the alkali ions reside between the S···S van der Waals gap of a ZrNCl type structure (R3m, a ~3.64 Å, c 29.48 Å). Structural characterization of the new phases and implications of the results are described.

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