Three Piperazine Complexes of Divalent Mercury: Hg(CF 3 ) 2 (Pip), Hg(SCN) 2 (Pip), and (Hg(SCN) 2 ) 2 (Pip)

Colourless single crystals of three piperazine (Pip) complexes of divalent mercury with ‐CF 3 and SCN ‐ as the ligands have been obtained from aqueous and ethanolic solution of the respective components Hg(CF 3 ) 2 , Hg(SCN) 2 , and piperazine. The crystal structures were determined by single crystal X‐ray diffraction: Hg(CF 3 ) 2 (Pip) ( 1 ) [monoclinic, C2/c, Z = 4, a = 891.2(1), b = 1649.8(2), c = 777.7(1) pm, β = 101.27(2)°, R 1 (all) = 0.0413], Hg(SCN) 2 (Pip) ( 2 ) tetragonal, P4 2 /ncm, Z = 4, a = 840.8(1), c = 1511.0(1) pm, R 1 (all) = 0.0479], (Hg(SCN) 2 ) 2 (Pip) ( 3 ) [triclinic, ${\rm P}{\bar 1}$ , Z = 1, a = 590.6(1), b = 738.6(2), c = 919.5(2) pm, α = 88.96(2)°, β = 82.80(2)°, γ = 78.21(2)°, R 1 (all) = 0.0582]. In 1 and 2 zig‐zag chains are observed with the piperazine molecule only weakly attached to the Hg(CF 3 ) 2 molecule. The Hg(SCN) 2 (Pip) chains in 2 condense to double chains in 3 where half of the piperazine molecules are missing. In both, 2 and 3 , Hg 2+ is coordinated in a distorted tetragonal fashion by two N and two S ligator atoms from piperazine and SCN ‐ ligands, respectively.