Ganguli, Ashok K. ; Corbett, John D. ; Kƪckerling, Martin (1998) Mixed cations for the stabilization of new features. Ca6.2Mg3.8Sn7, a phase with planar zigzag chains of interlinked square-planar tin units Journal of the American Chemical Society, 120 (6). pp. 1223-1229. ISSN 0002-7863
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Official URL: http://pubs.acs.org/doi/abs/10.1021/ja972812%2B
Related URL: http://dx.doi.org/10.1021/ja972812+
Abstract
The structure of orthorhombic Ca6.24(6)Mg3.76(6)Sn7 contains two types of chains built from edge- or face-sharing trigonal prisms of Ca and Mg atoms that are centered by Sn atoms. In one type, bonded zigzag 1∞ [Sn512−] chains are built of interconnected square-planar (D2h) Sn5 units. Alternating chains of condensed trigonal prismatic cations centered by isolated Sn atoms are interbonded to the first type through Sn-Ca,Mg interactions. The chain unit is two electrons richer than that for a simple Zintl-Klemm formalism for 1−, 2−, and 4-bonded Sn (4b-Sn0) because of the square-planar tin bonding. Band structure calculations within the extended Hückel formalism indicate the infinite tin chain alone is closed shell, but a metallic behavior (via open π-bonding) is produced by cation mixing in the full structure. Local bonding within square-planar Sn5 consists of normal s, px, py (σ) bonding, a single 4c-2e nonbonding MO on the outer tins, and a pz2 lone (π) pair. This new intermediate degree of hypervalency makes the unit isoelectronic with XeF42+. Property studies on powdered samples reveal a good metallic conduction but a small diamagnetism that is not uncharacteristic of heavy p-elements and their compounds.
Item Type: | Article |
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Source: | Copyright of this article belongs to American Chemical Society. |
ID Code: | 61948 |
Deposited On: | 16 Sep 2011 03:46 |
Last Modified: | 16 Sep 2011 03:46 |
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