Symmetrisation in the Interaction of Chloro[2‐(dimethylaminomethyl)phenyl‐C¹]mercury(II) with Thiosemicarbazone Derivatives of Pyridine‐2‐carboxamide and Pyrazin‐2‐carboxamide

Abstract

Pyridine‐ and pyrazine‐2‐carboxamide thiosemicarbazones (HAm4DH and HAmpz4DH) or their N4,N4‐dimethyl derivatives (HAm4DM and HAmpz4DM) react with chloro[2‐(dimethylaminomethyl)phenyl‐C1]mercury(II), [Hg(damp)Cl], to give the tetrahedral [Hg(TSC)2] complexes [TSC = Am4DH (1), Am4DM (2), Ampz4DH (3) or Ampz4DM (4)]. Spectroscopic studies and a X‐ray structural analysis show that the potentially tridentate thiosemicarbazones adopt S,N coordination modes, with each deprotonated thiosemicarbazone binding to the HgII centre through the azomethine nitrogen and the thiolate sulfur atoms, whereas the heterocyclic nitrogen atoms are free of coordination. Intra‐ and intermolecular hydrogen bonding in all complexes and specific C–H···π interactions with the chelate or pyridyl rings of the complexes 1 and 2 were found in the crystal structures. Furthermore, [Hg(damp)Cl] undergoes symmetrisation to give the symmetric unit [Hg(Hdamp)2]2+ in which the Hdamp is protonated at the nitrogen. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Zinc and mercury complexes of benzil bis(4-methyl-3-thiosemicarbazone)

“…4). The shift in chloroform is similar to those observed in other thiosemicarbazonate complexes containing a penta-coordinated mercury atom [22,34,36], and agrees with a dinuclear structure with a sulfur atom acting as a bridge between to metal centers, in which the mercury atom is penta-coordinated. This bridge should be broken in DMSO-d 6 since the signal is shifted to lower field, suggesting a lower coordination number.…”

“…The 199 Hg NMR is a useful tool to determine the metal environment, since the chemical shift is very sensitive to its coordination sphere. According to the literature, a decrease in the coordination number gives a greater deshielding [31][32][33][34][35] and therefore higher chemical shifts. The spectrum of complex 2 shows one signal at À917.8 ppm in DMSO-d 6 and at À898.3 ppm in DMF/CDCl 3 (Fig.…”

Bis[benzyl 3-(3-phenylprop-2-enylidene)dithiocarbazato-κ2N3,S]cadmium

“…For the isotypic Zn and Hg analogues, see: Fun et al (2008); Islam et al (2012). For the coordination behaviour of metal ions (Co, Ni, Cu, Zn, Cd and Hg) with the cinnamaldehyde Schiff base of S-methyldithiocarbazate, see: Liu et al (2009); Abram et al (2006). For the bioactivity of transition metal complexes of similar Schiff base ligands, see: Chew et al (2004); How et al (2008); Maia et al (2010).…”

Zn(II) and Hg(II) complexes of naphthalene based thiosemicarbazone: Structure and spectroscopic studies

“…Various well known chelating agents such as D-penicillamine (H 2 Pen@HSC(CH 3 ) 2 -CH(NH 3 ) + COO À ) and BAL (2,3-dimercaptopropanol) have been clinically used for detoxification and efficiently reduce plasma levels of Hg(II) [19][20][21]. Often, very stable forms include linear complexes with two sulfur ligands; nevertheless, the Hg-S bonds are labile and for higher coordination numbers the structures are flexible, often with distorted trigonal or tetrahedral coordination geometries [22][23][24][25][26]. However, limited number of Hg(II) and phynylmercury complexes with thiosemicarbazones are known, although they are good chelating candidate for this metal ion [22][23][24].…”