Bis(4-aminopyridinium) and bis(2-amino-6-methylpyridinium) cations stabilised by [MS sub(4)] sup(2-) anions: Synthesis, crystal structures, Hirshfeld surface analysis and sulfur transfer reactions

Abstract

Four new organic ammonium tetrasulfidometallates: (4-aminopyridinium)2[MoS sub(4)].H sub(2)O 1, (4-aminopyridinium)2[WS sub(4)].H sub(2)O 2, (2-amino-6-methylpyridinium) sub(2)[MoS sub(4)] 3, and (2-amino-6-methylpyridinium) sub(2)[WS sub(4)] 4 have been synthesized by a well-known base promoted cation exchange method. All compounds were characterized by elemental analysis, IR/Raman/UV-Vis spectroscopy, thermogravimetric analysis, and X-ray crystallography. The structures of 1 and 2 consist of unique tetrahedral [MoS sub(4)] sup(2-) and [WS sub(4)] sup(2-) dianions, which are charge-balanced by crystallographically independent 4-aminopyridinium monocations. Additionally, both have a lattice water molecule, which contributes to the overall stability of their structures. In compounds 3 and 4, 4-aminopyridinium of 1 and 2 are replaced by 2-amino-6-methylpyridinium cation and lack lattice water. The different H-bonding interactions viz N-H...S, C-H...S, N-H...O and O-H...O are observed in 1 and 2, which are reduced to two viz. N-H...S and C-H...S in 3 and 4. The weak interactions (N-H...O and O-H...O) originating from lattice water further interlink cations with [MoS sub(4)] sup(2-) and [WS sub(4)] sup(2-) anions forming extended networks in 1 and 2. To understand the importance of intermolecular interactions in the structures of 1-4, the Hirshfeld surface analyses were performed. The enrichment ratio (E) obtained in the structures of compounds 1-4 was obtained. Compounds 1-4 were tested for their sulfur transfer ability. Only compound 1 showed a predominant disulfide product formation in reaction with 1,3-dibromopropane.