Thiosemicarbazone Ligands

Iron(III) complexes of 2-acetylpyridine Af-oxide iV-methyl- and 3-azabicyclo[3.2.2.]nonylthiosemicarbazone, 24 and 25, respectively, have been isolated from both iron(III) perchlorate and chloride [117], The perchlorate salt yields low spin, octahedral, monovalent, cationic complexes involving two deprotonated, tridentate thiosemicarbazone ligands coordinated via the N-oxide oxygen, azomethine nitrogen and thiol sulfur based on infrared spectral studies. Their powder ESR g-values are included in Table 1 and indicate that bonding is less covalent than for the analogous thiosemicarbazones prepared from 2-acetylpyridine, 3a and 4. Starting with iron (III) chloride, compounds with the same cations, but with tetrachloroferrate(III) anions, were isolated. 

One of the few crystal structures solved for a metal complex of a heterocyclic thiosemicarbazone is bis(l-formylisoquinoline thiosemicarbazone) nickel(II) monohydrate, [Ni(21-H)2] (Fig. 5) [208]. The nickel(II) center was found to be NNS coordinated by two approximately planar thiosemicarbazone ligands. 

The basic thiosemicarbazone ligands coordinate in a N,S bidentate manner, generally via the azomethine N-donor and the thione or deprotonated amidothione group. Designating the ligands as HL, this usually results in square planar complexes [NiL2],1221-1227 [Ni(HL)2]X2,12 2,1228... 

Aliphatic thiosemicarbazones reveal varying coordination behavior dependent on the degree of deprotonation. The X-ray structure of the zinc complex of methyl pyruvate thiosemicarbazone shows different coordination of the two thiosemicarbazone ligands in the monomer, with one tridentate NOS and the other monodentate.868... 

Zinc complexes of cyclohexane-1,2-dione bis(thiosemicarbazone) have been formed in the neutral and doubly deprotonated form. The X-ray structures show distorted square-based pyramidal geometries for both complexes [ZnL(OH2)] and [Zn(H2L)Cl]Cl with the water or chloride occupying the axial position.886 The binuclear complex bis[l-phenylglyoxal bis(3-piperidylthiose-micarbazone)zinc] was synthesized by electrochemical methods and reveals a Zn2L2 with two tetradentate bis-thiosemicarbazone ligands bridging the metal centers.887... 

The Fe(III) complexes of R-substituted salicylaldehyde thiosemicarbazone (R-thsa2- Fig. 6) are among the most studied spin crossover materials of this family. The crystal structures of several of them have been determined at various temperatures. The iron-donor atom distances are compiled in Table 2. The Fe(III) ion is in a distorted FeS2N202 octahedron formed by two thiosemicarbazone ligands, which are geometrically arranged in such a way that the S and O atoms are located in cis positions, whereas the N atoms occupy trans positions, i.e. each tridentate molecule coordinates in an equatorial plane [101]. 

IR spectra were consistent with the structure shown for (92), where X = F, Cl, R = Me, Et.549 The IR spectra of square-planar-coordinated dimers LPtCl2PtL, where L = range of thiosemicarbazone ligands, show that L is 7V,.S -bidentate.550 IR data for Pt(II) complexes of bioactive thiosemicarbazones derived from 4-amino-antipyrine show that they are coordinated as N,N,S-donors.551... 

Kovala-Demertzi, D., Yadav, P.N., Dernertzis, M.A. et al. (2004) First use of apaUadium complex with a thiosemicarbazone ligand as catalyst precursor for the Heck reaction. Tetrahedron Lett., 45, 2923-6. 

A dissymmetric thiosemicarbazone ligand containing a hydrazonequi-noline arm, HaAMeTsQ and its chloride salt, [HsAMeTsQjCl, were synthesised. NMR spectroscopy together with X-ray diffraction... 

Nrrmala M, Manikandan R, Prakash G, Viswanathamurthi P (2014) Ruthenium(II) complexes of hybrid 8-hydroxyquinoline-thiosemicarbazone ligands synthesis, characterization and catalytic applications. Appl Organomet Chem 28(1) 18-26... 

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