Na 2 HgS 2 und K 2 HgS 2 , zwei Thiomercurate mit isolierten Anionen/Na 2 HgS 2 and K 2 HgS 2 , Two Thiomercurates with Discrete Anions

Na 2 HgS 2 and K 2 HgS 2 were obtained as colourless, tabular crystals by reacting the alkali sulfides Na 2 S and K 2 S with red HgS at 970 K. Both compounds are orthorhombic: Na 2 HgS 2 , oP40, s.g. Pbca with a = 18.24(2) Å, b = 7.494(5) Å, c = 7.237(5) Å, Z = 8; K 2 HgS 2 , oP20, s.g. Pbcm a = 10.697(6) Å, b = 7.958(8) Å, c = 7.272(9) Å, Z = 4. Their crystal structures were determined from four circle diffractometer data and refined anisotropically to conventional R-factors of 0.056 (Na 2 HgS 2 ) and 0.062 (K 2 HgS 2 ) for 945 and 485 reflections with F 0 2 > 3σ(F 0 2 ), resp. The crystal structures represent new structure types. They are closely related with each other and can be derived from hcp-arrays of the chalcogen-atoms. Characteristic feature is the formation of discrete, almost linear [S - Hs - S] 2- dithiomercurate anions with average HgS-bond lengths of 2.31 Å.