NaAuSe-A selenoaurate with cyclic anions

Abstract

Transparent deep orange crystals of NaAuSe were obtained by fusing together stoichiometric amounts of Na2Se, Au and Se at 730°C, followed by slow cooling of the melt. NaAuSe is tetragonal, tI48, space group I41/amd (No. 141), Z = 16 with a = 9.772(2)Å, c = 11.469(2)Å. The crystal structure was determined from single crystal diffractometer data and refined to a conventional R of 0.030 (276 Fo values, 20 variables). An outstanding feature of the crystal structure is the formation of discrete anions, which consist of V-shaped eight-membered rings, [Au4Se4]4−. Au is in an almost linear coordination by Se (∠Se-Au-Se: 168.31o, dAu-Se: 2.457(2)Å); the bond angle on Se is only 82.9(1)o. The crystal structure is based on a c.c.p.-packing of the chalcogen atoms.