Synthesis and crystal structures of HgFAsF6, Hg(HF)2(AsF6)2, Hg(HF)(AsF6)2 and Hg(AsF6)(SO3F)

•Diversity of Hg(II) coordination by F atoms in [AsF6]− salts: from six to nine.•Structure of HgFAsF6 represents a new structural type of MIIFXVF6 compounds.•In Hg(HF)2(AsF6)2, the Hg(II) is six-fold coordinated with very short Hg−FH bonds.•Crystal structure of Hg(HF)(AsF6)2 is isotypic with analogue Cd salt.•Hg(AsF6)(SO3F) is the first example of mixed-anion [AsF6]−/[SO3F]− compound.

The colourless HgFAsF6 was synthesized by oxidation of Hg2(AsF6)2 with elemental fluorine in anhydrous hydrogen fluoride. It crystallizes in the monoclinic space group P21/c with a=7.0645(3) Å, b=9.9023(3) Å, c=7.8686(3) Å, β=102.960(4)° V=536.43(3) Å3, and Z=4 at 150 K. The structure of HgFAsF6 consists of infinite zig-zag –[Hg–F–Hg]– chains oriented parallel to each other along the b axis and interconected by AsF6 groups. Hg(HF)2(AsF6)2 crystallizes in the triclinic space group P  1¯ with a=5.0781(3) Å, b=6.6907(5) Å, c=7.7135(5) Å, α=84.045(5), β=79.277(5)°, γ=80.612(6), V=253.32(3) Å3, and Z=1 at 150 K. The crystal structure is composed of infinite columns of Hg atoms linked by AsF6 groups. Each pair of adjacent Hg atoms is bridged by two AsF6 groups. The coordination of Hg is completed by two F atoms provided by HF molecules. Hg(HF)(AsF6)2 crystallizes in the monoclinic space group P21/c with a=9.4921(8) Å, b=9.2834(6) Å, c=10.5448(7) Å, β=103.795(7)°, V=902.53(12) Å3, and Z=4 at 150 K and it is isotypic to Cd(HF)(AsF6)2. The new mixed-anion compound Hg(AsF6)(SO3F) crystallizes in the monoclinic space group P21/c with a=5.1975(8) Å, b=18.046(3) Å, c=15.873(5) Å, β=93.614(13)°, V=1485.9(6) Å3, and Z=4 at 200 K. All three oxygen atoms from each SO3F group utilize for bonding with three Hg atoms. The Hg1 (Hg2) atoms are coordinated by two (four) oxygen atoms from two (four) SO3F groups and by six (three) fluorine atoms from AsF6 groups forming on that way tridimensional framework.

Graphical abstractDiversity of Hg(II) coordination by F atoms in HgFAsF6 and Hg(HF)n(AsF6)2 (n=1, 2) and the crystal structure of a new mixed-anion Hg(AsF6)(SO3F) compound Figure optionsDownload full-size imageDownload as PowerPoint slide