Synthesis,properties and structural characterization of 4-(2-ammonioethyl)piperazin-1-ium tetrasulfidotungstate hemihydrate and 1-ethylpiperazinediium tetrasulfidotungstate

The reaction of ammonium tetrasulfidotungstate with 2-piperazin-1-ylethanamine or 1-ethylpiperazine results in the formation of 4-(2-ammonioethyl)piperazin-1-ium tetrasulfidotungstate hemihydrate (C₆H₁₇N₃)WS₄]·½H₂O 1 or 1-ethylpiperazinediium tetrasulfidotungstate (C₆H₁₆N₂)WS₄] 2. The hemihydrate 1 can be dehydrated to the anhydrous compound (C₆H₁₇N₃)WS₄] 1a, which can be rehydrated to 1. Both 1 and 2 decompose to amorphous carbon containing tungsten disulphide. Compound 1 crystallizes in the centrosymmetric monoclinic space group C2/c, while compound 2 crystallizes in the centrosymmetric orthorhombic space group Pbca. The structures of 1 and 2 consist of a slightly distorted tetrahedral WS₄]^2? anion and 4-(2-ammonioethyl)piperazin-1-ium (1) or 1-ethylpiperazinediium dication (2) and additionally a lattice water in 1. In the crystal structure of 1 and 2 the organic cation and the WS₄]^2? anion are linked to each other via several weak N–H?S and C–H?S bonding interactions. The lattice water serves as a link between pairs of cations and pairs of anions with the aid of O–H?S and N–H?O interactions in compound 1.