CRYSTAL-STRUCTURE OF THE MERCURY(II) CRYP TATE [HG(CRYPTAND 222)][(HG(SCN)(3))(2)]CONTAINING A TRI(THIOCYANATO)MERCURATE(II) ANION WITH A CHAIN STRUCTURE

The reaction of [2.2.2]cryptand, 4,7,13,16,21,24-hexaoxa-1,10-diazabic yclo- [8.8.8]hexacosane, with mercuric thiocyanate yields crystals of [Hg(cryptand 222)][(Hg(SCN)(3))(2)]. The compound crystallizes monocli nically, space group C2/c, Z = 4, a = 2478.3(12), b = 1540.4(4), c = 1 049.4(3) pm, beta = 108.77(3)degrees. In the cation the mercury atom i s 8-coordinated by six oxygen and two nitrogen atoms with distances Hg -N 220(2) pm and Hg-O 268.8(9) pm (mean value). The polymeric anion co nsists of infinite chains -Hg-SCN-Hg- with bond distances Hg-S 254.2(4 ) and Hg-N 257(2) pm. Each Hg atom carries two additional terminal SCN ligands, with a mean Hg-S distance of 244(1) pm; the distance from Hg to the N atom of an SCN ligand of a neighbouring Hg atom is 300(2) pm , probably indicating an additional, although weak bonding.