Crystallographic and thermal investigations of organic ammonium tetrathiomolybdates

Abstract

The organic ammonium tetrathiomolybdates N-methylethylenediammonium tetrathiomolybdate (N-Me-enH(2))(MOS4) (1), N-(3-aminopropyl)propane-1,3-diaminium tetrathiomolybdate (dipnH(2))[MOS4](2), 4-(2-ammonioethyl)piperazin-1-ium tetrathiomolybdate hemihydrate (2-pipH-1-EtNH3)[MOS4]center dot 1/2H(2)O (3) and 2,2'-iminodiethanaminium tetrathiomolybdate (dienH(2))[MOS4](4), were synthesized by an aqueous reaction of ammonium tetrathiomolybdate with the organic amines N-methylethylenediamine (N-Me-en), bis(3-aminopropyl)amine(dipn), 2-piperazin-1-ylethanamine(2-pip-1-EtNH2) and bis(2-aminoethyl)amine (dien), respectively. All compounds were characterized by elemental analysis, H-1 NMR, IR, Raman and U-V-Vis spectra, and the crystal structures of compounds 1-3 were determined. The structures of 1-3 consist of diprotonated organic cations, which are linked to the tetrahedral [MOS4](2-) anions with the aid of several weak H-bonding interactions. The MOS4 tetrahedron in all compounds is slightly distorted with one or more Mo-S bonds being elongated, which can be attributed to the H-bonding interactions. The difference A between the longest and the shortest Mo-S bond lengths for 1-3 are 0.0379, 0.0186 and 0.0302 angstrom, respectively. Unlike I and 2, which are anhydrous, compound 3 is a hemihydrate. The water molecule in 3 occupies the pores between alternating layers of the cations and anions in the crystallographic bc-plane. Compound 3 exhibits four types of weak H-bonding interactions namely N-H...S, N-H...O, O-H...S and C-H.S. All four tetrathiomolybdates decompose endothermically forming amorphous disulfides containing C and N. A comparative structural description of 28 tetrathiomolybdates is presented.