Syntheses, characterization and thermal properties of [M(Spy)2(SpyH)2] (M=Cd and Hg; Spy−=pyridine-4-thiolate; SpyH=pyridinium-4-thiolate)) and [M(SpyH)4](ClO4)2 (M=Zn, Cd and Hg)

The complexes [M(Spy)2(SpyH)2] (Spy−=pyridine-4-thiolate; M=Cd (1) and Hg (2)), of a hitherto unknown type, were prepared by reacting the corresponding metal perchlorates with pyridine-4-thiol in the ratio 1:6 in DMSO–MeOH. The cations [M(SpyH)4]2+ (M=Zn, Cd and Hg) were prepared by a similar reaction, but with M–pySH=1:4 in MeOH, and isolated as their perchlorate salts, 3, 4 and 5. The structures of 1–5 were determined by X-ray crystallography. Both compounds 1 and 2, and the cations in 3–5, are mononuclear complexes in which the metal centre adopts a distorted MS4 kernel. Intermolecular NH⋯N hydrogen bonds in 1 and 2 lead to one dimensional polymeric chain structures, and similarly NH⋯O⋯HN hydrogen bonds between the cations and anions in 3–5 result in chain structures. Thermogravimetric and pyrolysis experiments demonstrate that 1 and 2 decompose to give the corresponding metal sulfides. Metal (113Cd/199Hg (as appropriate)) NMR spectra have been measured for solutions of 4 and 5 with and without incremental addition of NaOMe. Separate signals were not observed for [M(SpyH)n(Spy)4−n](n−2)+, even at the lowest accessible temperature. The changes in metal NMR chemical shift as [M(SpyH)4]2+ is converted into [M(Spy)4]2− are surprisingly small.