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. © 2001 Elsevier Science B.V.