Schiff bases derived from mercury(II)–aminothiolate complexes as metalloligands for transition metals

Mercury(II) complexes of aromatic aminothiolate ligands of formula [Hg(n-SC6H4NH2)2], n=3 (1) or 4 (2) and [RHg(n-SC6H4NH2)], R=Me, n=3 (3) or 4 (4); R=Ph, n=3 (5) or 4 (6) have been obtained and characterized by infrared and 1H, 13C and 199Hg-NMR spectroscopies. The latter indicates that, in solution, complexes 1–6 have an essentially linear coordination about Hg(II). Unprecedented Schiff bases containing the Hg–S(thiolate) bond have been synthesized from 3–6 and salicylaldehyde yielding complexes of formula [RHg(n-SC6H4NCHC6H4OH)], R=Me, n=3 (7) or 4 (8); R=Ph, n=3 (9) or 4 (10). The template reaction of 3 and 4 with M(CH3COO)2, M=Zn(II), Cd(II), and salicylaldehyde has afforded trimetallic complexes of formula [MII{MeHg(n-SC6H4NCHC6H4O)}2], M=Zn, n=3 (11) or 4 (12); M=Cd, n=3 (13) or 4 (14). Complexes 7–14 have also been explored by use of infrared and NMR spectroscopies. The crystal structure determination of 2, 3, 5, 7 and 8 by X-ray diffraction shows that Hg(II) has an essentially linear coordination. The presence of additional secondary Hg⋯S interactions in all these complexes leads to an increase in the coordination number of Hg to 4 or 5. In 2, the interaction of each S–Hg–S unit with three neighbouring units gives rise to a polymeric chain, which can be considered as being formed by pairs of fused incomplete cubanes. In 3, 5, 7 and 8, secondary Hg⋯S bonds between pairs of C–Hg–S fragments yield Hg2S2 dimers. In 3, these dimers afford two-dimensional sheets by means of additional Hg⋯N secondary interactions. The crystal packing of the Hg2S2 dimers in 5, 7 and 8 is very similar and gives rise to one-dimensional chains by means of additional Hg⋯S bonds. The resulting polymeric zig-zag ladders can be described as formed by Hg4S4 pseudo-cubanes sharing opposite faces.