Synthesis, structure and properties of SrAu3In3 and EuAu3In3—New indides with gold zig-zag chains

The Gold-rich Indide Eu5Au17.7In4.3 and its Relation with the Structures of SrAu4.76In1.24 and BaLi4

“…The Au-In distances range from 283 to 309 pm. The shorter ones compare well with the sum of the covalent radii [13] of 284 pm, and they are in a range similar to those of the other europium gold indides [4,6,11,12].…”

“…The Eu-Au distances range from 310 to 339 pm, close to the sum of the covalent radii [13] of 319 pm. Also in EuAuIn [6] (317 -334 pm), EuAuIn 2 [12] (317 -332 pm), Eu 2 Au 3 In 4 [11] (305 -351 pm), and EuAu 3 In 3 [4] (334 -338 pm) the europium sites have gold atoms as closest neighbors, since the Pauling electronegativity [13] of gold (2.54) is significantly higher than that of indium (1.78). The Eu1 (478 pm Eu1-Eu3) and Eu2 (546 pm Eu2-Eu1) atoms have no close Eu-Eu contacts.…”

“…In 3 (279 pm) [4] and fcc gold (288 pm Au-Au) [21], and one can therefore assume significant bonding. The Au-In distances range from 283 to 309 pm.…”

“…The structural chemistry and the magnetic properties are goverened by a stable 4 f 7 Eu II ground state and in some cases additionally by Au-Au d 10 -d 10 interactions or even by extended Au-Au bonding. To give some examples, secondary Au-Au interactions are the driving force for superstructure formation of EuAuGe (316 pm) [2] and EuAuSn (334 -335 pm) [3], while Au-Au zig-zag chains (279 pm) occur in EuAu 3 In 3 [4].…”

“…The polyanionic networks show strong covalent Au-In besides In-In bonding in the indium-richer phases Eu 2 -Au 3 In 4 and EuAuIn 2 . So far, Au-Au bonding was only observed within the zig-zag chains of EuAu 3 -In 3 [4]. Since Eu 2+ (112 pm) and Sr 2+ (127 pm) have comparable ionic radii [13], and keeping the peculiar crystal structures of the gold-rich phases SrAu 4.76 In 1.24 [14] and Sr 5 Au 13.5 In 8.5 [15] in mind, we were interested also in the gold-rich part of the Eu-Au-In system.…”