A B C
Z. Naturforsch. 2013, 68b, 10 – 16
doi:10.5560/ZNB.2013-2296
The Stannides RE2Ni2Sn (RE = Pr, Ho, Er, Tm) – Structural Transition from the W2B2Co to the Mo2B2Fe Type as a Function of the Rare Earth Size
Birgit Heying1, Ute Ch. Rodewald1, Bernard Chevalier2, and Rainer Pöttgen1
1 Institut für Anorganische und Analytische Chemie, Universität Münster, Corrensstrasse 30, 48149 Münster, Germany
2 CNRS, Université de Bordeaux, ICMCB, 87 Avenue Dr. A. Schweitzer, F-33608 Pessac-Cedex, France
Reprint requests to R. Pöttgen. E-mail: pottgen@uni-muenster.de
Received November 19, 2012 / published online January 10, 2013
The stannides RE2Ni2Sn (RE = Pr, Ho, Er, Tm) were synthesized by arc-melting of the elements and characterized by powder X-ray diffraction. Pr2Ni2Sn crystallizes with the orthorhombic W2B2Co-type structure, Immm, a = 443.8(1), b = 572.1(1), c = 855.1(2) pm, wR2 = 0.0693, 293 F2 values, 13 variables. A structural transition to the tetragonal Mo2B2Fe type occurs for the heavier rare earth elements. The structures of Ho2Ni2Sn (a = 729.26(9), c = 366.66(7) pm, wR2 = 0.0504, 250 F2 values, 12 variables), Er2Ni2Sn (a = 727.2(2), c = 364.3(1) pm, wR2 = 0.0397, 262 F2 values, 12 variables), and Tm2Ni2Sn (a = 725.2(1), c = 362.8(1) pm, wR2 = 0.0545, 258 F2 values, 12 variables) were refined from single-crystal diffractometer data. The switch in structure type is driven by the size of the rare earth element. The [Ni2Sn] substructures are composed of Ni2Sn2 squares and Ni4Sn2 hexagons in Pr2Ni2Sn, and of Ni3Sn2 pentagons in Er2Ni2Sn. The Ni4Sn2 hexagons and Ni3Sn2 pentagons exhibit Ni2 pairs with Ni–Ni distances of 247 pm in Pr2Ni2Sn, and of 250 pm in Er2Ni2Sn.
Key words: Stannides, Crystal Structure, Lanthanoid Contraction
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