Variability in the Coordination Modes of 2‐Pyridineformamide Thiosemicarbazone (HAm4DH) in some Zinc(II), Cadmium(II), and Mercury(II) Complexes

Abstract

The reduction of 2-cyanopyridine by sodium in dry methanol in the presence of thiosemicarbazide produces 2-pyridineformamide thiosemicarbazone, HAm4DH. The reactions of the potentially tridentate ligand HAm4DH with salts of Zn, Cd, and Hg gave a variety of metal-ligand complexes. The complexes were characterized by mass spectrometry as well as IR and multinuclear NMR ( 1 H, 13 C, 13 C CP/MAS, 113 Cd, 199 Hg) spectroscopy. The crystal structures of [Zn(Am4DH)(OAc)] 2 ·H 2 O, [Hg(HAm4DH) 2 Br 2 ]·C 2 H 5 OH and 1 ϱ [Hg(μ-S-Am4DH)Br] were obtained. Coordination of anionic Am4DH Ϫ occurs through the pyridyl nitrogen, imine nitrogen and thiolato sulfur atoms, while 2011 the neutral ligands in [Hg(HAm4DH) 2 Br 2 ] coordinate as monodentate ligands through their thione sulfur atoms. One of the acetate ligands in [Zn(Am4DH)(OAc)] 2 ·H 2 O is bridging monodentate and the other bridging bidentate. 1 ϱ [Hg(μ-S-Am4DH)Br] features five-coordinate mercury centers with bridging thiolato sulfur atoms. The intermolecular arrangement is dictated by hydrogen bonding from the amino groups and by π-π stacking of the pyridine rings.complexes of 2-pyridineformamide thiosemicarbazone (Fig. 1). The compounds were characterized by elemental analysis, IR and multinuclear NMR ( 1 H, 13 C, 13 C CP/MAS, 113 Cd, 199 Hg) spectroscopy, mass spectrometry and, in some cases, X-ray diffraction. The crystal and molecular structures of a binuclear zinc(II) complex and two mercury(II) complexes are included.

Metal Complexes of Acetone Thiosemicarbazone: Synthesis, Spectral Characterization and Pharmacological Studies

“…A negative shift of the order 31-42 cm -1 was observed for C=N stretching vibration on coordination due to the decrease of the bond order as a result of metal nitrogen bond formation which is in agreement with the work reported by [21][22]. The next strong band at 866-788 cm -1 is attributed to C=S group, a negative shift in the region of 864-717 and 854-719 cm -1 was observed in the complexes on coordination thereby indicating the involvement of thio sulfur in the coordination the metal ion [21,22,6 ]. The bands in the range 3481-3416 and 3377-3047 cm -1 are attributed to ν(OH, H2O) and ν(NH, NH2).…”

“…On the other hand, the spectra of the complexes showed new bands around 530-530, 430-448 and 414-447 cm -1 due to νM-O, νM-N and νM-S respectively [21][22][23]. The presence of these bands supported the formation of the complexes.…”

“…The infrared spectra of ACTSC ligand Table 3 showed a strong band at 1645 cm -1 attributed to C=N group [20][21].…”

Supramolecular Architecture in Gold(I) and Gold(III) 2-Pyridineformamide Thiosemicarbazone Complexes by Secondary Interactions: Synthesis, Structures, and Luminescent Properties

“…In the 1 H NMR spectra, the pyridine proton signals appear at 7.60–8.70 ppm (within their normal range), the N(4)H signals of 1 appear at 8.05 ppm, and those of the N(5)H protons of both complexes appear at 9.10 ppm, that is, downfield from their counterparts in the spectra of the ligands and other complexes of these thiosemicarbazones. ,,, Furthermore, in the case of 1 these signals are downfield from the N(4)H signals, which is quite unusual for this kind of thiosemicarbazone. The hydrazinic proton signal of 1 appears downfield from its position in HAm4DH (10.05 ppm), at 11.07 ppm; this is not sufficiently low field to suggest intramolecular hydrogen bonding (so compound 1 seems to retain the E configuration of the uncoordinated ligand, with the hydrazinic proton on N(3); see Scheme ) but is low enough field to suggest hydrogen bonding with the solvent.…”

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

“…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.…”