Thiosemicarbazides metal complexes

The coordination shell comprises three fac-S and three fac-N-donor atoms in [Fe(6mp)3] [FeClJCl, where 6mp = 6-thiopurine, (189). Both iron(II) and iron(III) complexes are included in a review of transition metal complexes of thiosemicarbazones. " 5,5 -Dimethyl-l,2,3-cyclohex-anetrione-l,2-dioxime-3-thiosemi-carbazone, dcdt (190), acts as an A, A, 5 -donor to Fe +, giving a bis-ligand complex (contrast [Fe(7V,7V -dcdt)3] with Fe " "). The Schiff bases from pyridine 2-carboxaldehyde and thiosemicarbazide or 4-phenyl thiosemicarbazide also act as A, VV, 5 -donors, both to Fe " " and to Fe " ". The antibacterial activity of these complexes was assessed, in... 

Burrows. A.D. Mingos. D.M.P. White. A.J.P. Williams. D.J. Crystal engineering of metal complexes based on charge-augmented double hydrogen-bond interactions between thiosemicarbazides and carboxylates. Chem. Commun. 1996, (1). 97-99. 

The metallic complexes are prepared in two steps (a) preparation of the heterocyclic ligand 1,5-diaminotetrazole and (b) preparation of the final complex. 1,5-Diaminotetrazole is prepared by the reaction of thiosemicarbazide, sodium azide, and lead monoxide in a dimethylformamide solvent [48]. 

Thiosemicarbazides (TSC) and thiosemicarbazones generally react with transition metal ions to form chelate complexes by bonding through both the sulfur and the hydrazinic nitrogen atoms. With silver(I) however, they appear to behave as monodentate ligands and bond through the sulfur atom only.436... 

In view of its zinc content, the activity of yeast ADH was studied in the presence of a large variety of agents known to combine with this metal ioii in simple systems as salts, chelates, or complex ions. It was expected that the formation of such compounds would reduce the activity of the enzyme if zinc were involved in its mechanism of action. In addition to OP, aa D, 8-OHQ-5SA, DZ, and TU (Vallee and Hoch, 1955), the following have since been found to inhibit yeast ADH activity NaDDC, BAL, Cupferron, thiosemicarbazide, sodium sulfide, potassium cyanide, and sodium azide (Vallee and Hoch, in preparation for publication). Inhibition was found to be strongly dependent upon the time of contact between the enzyme and the inhibitor prior to the measurement of activity, the pH of the preincubation mixture, and the temperature at which the preincubation was allowed to take place. 

EDTA (ethylenediaminetetraacetic acid) forms stable metal chelates with a number of metal ions. Using this reagent as a complexing- agent, arsenic, bismuth, and selenium can be determined without any interference in the presence of nickel and cobalt. The cobalt-EDTA chelate is stable in 5 M HCl solution, whereas the corresponding bismuth complex is not. The influence of copper on the determination of arsenic can also be eliminated with EDTA, but not in the determination of selenium. Thiourea has been used to eliminate the influence of copper in the determination of antimony and sodium oxalate to eliminate the influence of copper and nickel in the determination of tin. An addition of thiosemicarbazide and 1,10-phenanthro-line reduces the interference of copper, nickel, platinum, and palladium in the determination of arsenic. 

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