Synthesis and structural characterization of two new non-centrosymmetric tetrasulfidometalates

Abstract

The synthesis and structural characterization of two new group VI tetrasulfidometalates (NH4)6[MS4]3.(hmt)4 [hmt = hexamethylenetetramine; M = W (1); M = Mo (2)] is reported. 1 and 2 are isostructural and crystallize in the non-centrosymmetric trigonal space group R3c. The (NH4)+ cations, [MS4]2- anions, and hmt molecules are joined by hydrogen bonding to form a three-dimensional network. In the crystal structure six NH4+ ions and six [MS4]2- anions are arranged to form channels running along [001] hosting a part of the hmt molecules. The channels are surrounded by the remaining hmt molecules. The presence of hmt in the structures of 1 or 2 results in a reduction of the decomposition temperature compared to that of (NH4)2[MS4] and formation of carbon contaminated metal sulfide residues.