Campus Units

Chemistry

Document Type

Article

Publication Version

Published Version

Publication Date

2014

Journal or Book Title

Journal of the American Chemical Society

Volume

136

Issue

8

First Page

3108

Last Page

3117

DOI

10.1021/ja411150e

Abstract

A new homologous series of intermetallic compounds containing three-dimensional (3-d) tetrahedral frameworks of gold atoms, akin to hexagonal diamond, have been discovered in four related Sr–Au–Al systems: (I) hexagonal SrAl3–xAu4+x (0.06(1) ≤ x ≤ 0.46(1), P6̅2m, Z = 3, a = 8.633(1)–8.664(1) Å, c = 7.083(2)–7.107(1) Å); (II) orthorhombic SrAl2–yAu5+y (y ≤ 0.05(1); Pnma, Z = 4, a = 8.942(1) Å, b = 7.2320(4) Å, c = 9.918(1) Å); (III) Sr2Al2–zAu7+z (z = 0.32(2); C2/c, Z = 4, a = 14.956(4) Å, b = 8.564(2) Å, c = 8.682(1) Å, β = 123.86(1)°); and (IV) rhombohedral Sr2Al3–wAu6+w (w ≈ 0.18(1); Rc, Z = 6, a = 8.448(1) Å, c = 21.735(4) Å). These remarkable compounds were obtained by fusion of the pure elements and were characterized by X-ray diffraction and electronic structure calculations. Phase I shows a narrow phase width and adopts the Ba3Ag14.6Al6.4-type structure; phase IV is isostructural with Ba2Au6Zn3, whereas phases II and III represent new structure types. This novel series can be formulated as Srx[M3]1–xAu2, in which [M3] (= [Al3] or [Al2Au]) triangles replace some Sr atoms in the hexagonal prismatic-like cavities of the Au network. The [M3] triangles are either isolated or interconnected into zigzag chains or nets. According to tight-binding electronic structure calculations, the greatest overlap populations belong to the Al–Au bonds, whereas Au–Au interactions have a substantial nonbonding region surrounding the calculated Fermi levels. QTAIM analysis of the electron density reveals charge transfer from Sr to the Al–Au framework in all four systems. A study of chemical bonding by means of the electron-localizability indicator indicates two- and three-center interactions within the anionic Al–Au framework.

Comments

Reprinted (adapted) with permission from J. Am. Chem. Soc., 2014, 136 (8), pp 3108–3117. Copyright 2014 American Chemical Society.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

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