Crystal Growth from Anhydrous HF Solutions of M(2+) (M = Ca, Sr, Ba) and [AuF(6)](−), Not Only Simple M(AuF(6))(2) Salts

[Image: see text] Crystal growth from anhydrous HF solutions of M(2+) (M = Ca, Sr, Ba) and [AuF(6)](−) (molar ratio 1:2) gave [Ca(HF)(2)](AuF(6))(2), [Sr(HF)](AuF(6))(2), and Ba[Ba(HF)](6)(AuF(6))(14). [Ca(HF)(2)](AuF(6))(2) exhibits a layered structure in which [Ca(HF)(2)](2+) cations are connected by AuF(6) units, while the crystal structure of Ba[Ba(HF)](6)(AuF(6))(14) exhibits a complex three-dimensional (3-D) network consisting of Ba(2+) and [Ba(HF)(2)](2+) cations bridged by AuF(6) groups. These results indicate that the previously reported M(AuF(6))(2) (M = Ca, Sr, Ba) compounds, prepared in the anhydrous HF, do not in fact correspond to this chemical formula. When the initial M(2+)/[AuF(6)](−) ratio was 1:1, single crystals of [M(HF)](H(3)F(4))(AuF(6)) were grown for M = Sr. The crystal structure consists of a 3-D framework formed by [Sr(HF)](2+) cations associated with [AuF(6)](−) and [H(3)F(4)](−) anions. The latter exhibits a Z-shaped conformation, which has not been observed before. Single crystals of M(BF(4))(AuF(6)) (M = Sr, Ba) were grown when a small amount of BF(3) was present during crystallization. Sr(BF(4))(AuF(6)) crystallizes in two modifications. A high-temperature α-phase (293 K) crystallized in an orthorhombic unit cell, and a low-temperature β-phase (150 K) crystallized in a monoclinic unit cell. For Ba(BF(4))(AuF(6)), only an orthorhombic modification was observed in the range 80–230 K. An attempt to grow crystals of Ca(BF(4))(AuF(6)) failed. Instead, crystals of [Ca(HF)](BF(4))(2) were grown and the crystal structure was determined. During prolonged crystallization of [AuF](6)(–) salts, moisture can penetrate through the walls of the crystallization vessel. This can lead to partial reduction of Au(V) to A(III) and the formation of [AuF(4)](−) byproducts, as shown by the single-crystal growth of [Ba(HF)](4)(AuF(4))(AuF(6))(7). Its crystal structure consists of [Ba(HF)](2+) cations connected by AuF(6) octahedra and square-planar AuF(4) units. The crystal structure of the minor product [O(2)](2)[Sr(HF)](5)[AuF(6)](12)·HF was also determined.