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 I 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 I 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 I and 2 decompose to give the corresponding metal sulfides. Metal (Cd-113/Hg-199 (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. (C) 2003 Elsevier B.V. All rights reserved.