Magnesium intermetallics: synthesis and structure of Eu2Pt2Mg and Sr2Pt2Mg
Author:
Reimann Maximilian Kai1, Pöttgen Rainer1
Affiliation:
1. Institut für Anorganische und Analytische Chemie , Universität Münster , Corrensstrasse 30 , 48149 Münster , Germany
Abstract
Abstract
The intermetallic phases Sr2Pt2Mg and Eu2Pt2Mg were obtained by reaction of the elements in sealed tantalum tubes at high temperature. Sr2Pt2Mg crystallizes with the monoclinic Ca2Ir2Si type (C2/c, a = 1020.7(7), b = 597.7(4), c = 827.0(4) pm, β = 103.37(5)°), while Eu2Pt2Mg adopts the orthorhombic W2CoB2-type structure (Immm, a = 440.31(5), b = 582.20(6), c = 914.11(9) pm, wR = 0.0359, 277 F
2 values, 14 variables). The magnesium atoms in both structures are coordinated by four Pt2 dumb-bells with a rectangular planar coordination in Eu2Pt2Mg (268 pm Pt–Mg) and a distorted tetrahedral one in Sr2Pt2Mg (273–275 pm Pt–Mg). The Pt–Pt distances are 277 pm in the europium and 269 pm in the strontium compound. The polyanionic [Pt2Mg] units are planar in Eu2Pt2Mg and separated by the europium atoms. The Sr2Pt2Mg structure shows the motif of hexagonal rod packing for the [Pt2Mg] rows that are embedded in a strontium matrix. Chemical bonding and the influence of the valence electron count on the formation of the structure types are discussed.
Publisher
Walter de Gruyter GmbH
Subject
General Chemistry
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