Zinc(II) complexes of 2,4-dithiobiuret

The zinc(II) complexes of 2,4-dithiobiuret (Hdtb = L) ZnL₂X₂ (X = Cl, Br, I) and ZnL_xA₂ (A = NO₃ and SO₄/2, x = 2.5; A = ClO₄, x = 2) have been prepared and investigated by conductometric, i.r. and Raman methods. In these compounds Hdtb behaves as S-monodentate in the ZnL₂X₂ and as S,S-bidentate ligand in the ZnL_xA₂ complexes.     

Complexes of cadmium(II) with 2,4-dithiobiuret

The cadmium(II) complexes of 2,4-dithiobiuret (Hdtb=L) : Cd₂L₃Cl₄, CdL₂X₂ (X=Br, I, ClO₄), CdL₃SO₄·H₂O and CdL₄(NO₃)₂ have been prepared and investigated by i.r. spectra. In all these complexes Hdtb is S-coordinated, principally behaving as a monodentate ligand, in some cases with a weaker interaction of the second thiocarbonylic sulphur atom. In the halide complexes the cadmium ion is six coordinated with halide bridging ions.     

Iron(II) and iron(III) complexes containing ethynyl thiophene fragments

The synthesis of the new complexes Cp*(dppe)FeCC2,5-C₄H₂SR (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; dppe = 1,2-bis(diphenylphosphino)ethane; 2a, R = CCH; 2b, R = CCSi(CH₃)₃; 2c, R = CCSi(CH(CH₃)₂)₃; 3a, R = CC2,5-C₄H₂SCCH; 3c, R = CC2,5-C₄H₂SCCSi(CH(CH₃)₂)₃) is described. The ¹³C NMR and FTIR spectroscopic data indicate that the π-back donation from the metal to the carbon rich ligand increases with the size of the organic π-electron systems. The new complexes were also analyzed by CV and the chemical oxidation of 2a and 3c was carried out using 1 equiv of [Cp₂Fe][PF₆]. The corresponding complexes 2a[PF₆] and 3c[PF₆] are thermally stable, but 2a[PF₆] was too reactive to be isolated as a pure compound. The spectroscopic data revealed that the coordination of large organic π-electron systems to the iron nucleus produces only a weak increase of the carbon character of the SOMO for these new organoiron(III) derivatives.     

Copper(I) coordination in the 2,4-dithiobiuret complexes

The new 2,4-dithiobiuret (Hdtb) complexes Cu(Hdbt)X·DMF (X = Cl, Br, I), Cu(Hdtb)₂A (A = ClO₄, NO₃, Cl) and Cu₂(Hdtb)₃SO₄ have been prepared. The crystal structure of the Cu(Hdtb)Cl·DMF complex has been determined: copper atom has a trigonal pyramidal coordination with three short basal bonds Cu(S, S, Cl) and one axial longer CuS bond. Two ν(CuS) and one ν(CuX) band have been identified in the i.r. spectra of the Cu(Hdtb)X·DMF complexes and two ν(CuS) bands in the spectra of the Cu(Hdtb)₂A and Cu₂(Hdtb)₃SO₄ complexes. The Cu(Hdtb)X (X = Cl, Br, I) complexes have been prepared again from ethanol solutions in different conditions and show three types (A, B, C) of far-i.r. spectra. The chloride always shows the (A) type. The bromide shows both the (A) and (B) types depending on the preparation conditions (presumably the Cu/L ratio used in the preparation). A transition from the (A) to the (B) type is observed in the solid state at room temperature for the bromide complex. A tentative explanation of this fact is discussed. The CuLI complex prepared at room temperature shows only the type (B) spectrum but prepared at 80°C shows a third far-i.r. spectrum (C). It is confirmed that in all the Cu(Hdtb)X (X = Cl, Br, I) complexes the ligand is S,S-coordinated to the metal.     

Spin transition in iron(III) and iron(II) complexes

The main stages of the studies on the spin transitions in iron(III) and iron(II) complexes are considered. The types of the spin transitions and the factors responsible for the latter are reported. The problems arising during experiments in this field are discussed.     

Solid complexes of iron(II) and iron(III) with rutin

Solid complex compounds of Fe(II) and Fe(III) ions with rutin were obtained. On the basis of the elementary analysis and thermogravimetric investigation, the following composition of the compounds was determined: (1) FeOH(C₂₇H₂₉O₁₆)·5H₂O, (2) Fe₂OH(C₂₇H₂₇O₁₆)·9H₂O, (3) Fe(OH)₂(C₂₇H₂₉O₁₆)·8H₂O, (4) [Fe₆(OH)₂(4H₂O)(C₁₅H₇O₁₂)SO₄]·10H₂O. The coordination site in a rutin molecule was established on the basis of spectroscopic data (UV–Vis and IR). It was supposed that rutin was bound to the iron ions via 4C=O and 5C—oxygen in the case of (1) and (3). Groups 5C–OH and 4C=O as well as 3′C–OH and 4′C–OH of the ligand participate in binding metals ions in the case of (2). At an excess of iron(III) ions with regard to rutin under the synthesis conditions of (4), a side reaction of ligand oxidation occurs. In this compound, the ligands’ role plays a quinone which arose after rutin oxidation and the substitution of Fe(II) and Fe(III) ions takes place in 4C=O, 5C–OH as well as 4′C–OH, 3′C–OH ligands groups. The magnetic measurements indicated that (1) and (3) are high-spin complexes.     

Gaseous iron(II) and iron(III) complexes with BINOLate ligands

Electrospray ionization (ESI) of dilute solutions of 1,1'-bi-2-naphthol (BINOL) and iron(II) or iron(III) sulfate in methanol/water allows the generation of monocationic complexes of iron and deprotonated BINOL ligands with additional methanol molecules in the coordination sphere, and the types of complexes formed can be controlled by the valence of the iron precursors used in ESI. Thus, iron(II) sulfate leads to [(BINOLate)Fe(CH3OH)n]+ complexes (n=0-3), whereas usage of iron(III) sulfate allows the generation of [(BINOLdiate)-Fe(CH3OH)n]+ cations (n=0-2); here, BINOLate and BINOLdiate stand for singly and doubly deprotonated BINOL, respectively. Upon collision-induced dissociation, the mass-selected ions with n>0 first lose the methanol ligands and then undergo characteristic fragmentations. Bare [(BINOLdiate)Fe]+, a formal iron(III) species, undergoes decarbonylation, which is known as a typical fragmentation of ionized phenols and phenolates either as free species or as the corresponding metal complexes. The bare [(BINOLate)Fe]+ cation, on the other hand, preferentially loses neutral FeOH to afford an organic C20H12O+* cation radical, which most likely corresponds to ionized 1,1'-dinaphthofurane.     

Polarographic determination of iron(II) and iron(III) complexes with edta

The iron(II) and iron(III) complexes with EDTA can be determined separately and in mixtures in acetate-buffered medium at pH 4.0. The E_{$\text{1}\text{2}$}values are in the range ?0.105 to ?0.112 V vs. SCE. Linear calibration plots are obtained over the range 0–1.0 mM for each oxidation state. A sample-handling procedure for avoiding oxidation of iron(II) species is described. It is shown that the acetate buffer system does not affect the stability of the iron-EDTA complexes.     

Facile ring opening of iron(III) and iron(II) complexes of meso-amino-octaethylporphyrin by dioxygen

Pyridine solutions of ClFe(III)(meso-NH(2)-OEP) undergo oxidative ring opening when exposed to dioxygen. The high-spin iron(III) complex, ClFe(III)(meso-NH(2)-OEP), has been isolated and characterized by X-ray crystallography. In the solid state, it has a five-coordinate structure typical for high-spin (S = 5/2) iron(III) complex. In chloroform-d solution, ClFe(III)(meso-NH(2)-OEP) displays an (1)H NMR spectrum characteristic of a high-spin, five-coordinate complex and is unreactive toward dioxygen. However, in pyridine-d(5) solution a temperature-dependent equilibrium exists between the high-spin (S = 5/2), six-coordinate complex, [(py)ClFe(III)(meso-NH(2)-OEP)], and the six-coordinate, low spin (S = 1/2 with the less common (d(xz)d(yz))(4)(d(xy))(1) ground state)) complex, [(py)(2)Fe(III)(meso-NH(2)-OEP)](+). Such pyridine solutions are air-sensitive, and the remarkable degradation has been monitored by (1)H NMR spectroscopy. These studies reveal a stepwise conversion of ClFe(III)(meso-NH(2)-OEP) into an open-chain tetrapyrrole complex in which the original amino group and the attached meso carbon atom have been converted into a nitrile group. Additional oxidation at an adjacent meso carbon occurs to produce a ligand that binds iron by three pyrrole nitrogen atoms and the oxygen atom introduced at a meso carbon. This open-chain tetrapyrrole complex itself is sensitive to attack by dioxygen and is converted into a tripyrrole complex that is stable to further oxidation and has been isolated. The process of oxidation of the Fe(III) complex, ClFe(III)(meso-NH(2)-OEP), is compared with that of the iron(II) complex, (py)(2)Fe(II)(meso-NH(2)-OEP); both converge to form identical products.     

Iron(III) and nickel(II) template complexes derived from benzophenone thiosemicarbazones

New iron(III) and nickel(II) chelates were synthesized by template reaction of 2,4-dihydroxy- and 2-hydroxy-4-methoxy-benzophenone S-methylthiosemicarbazones with 2-hydroxy- and 5-bromo-2-hydroxy-benzaldehydes. The template complexes were isolated as stable solids and characterized by elemental analysis, conductivity and magnetic measurements, IR, ¹H NMR, UV–Visible, and mass spectra. The crystal structure of N ¹-(2-hydroxy-4-methoxyphenyl)(phenyl)methylene-N ⁴-(2-hydroxy-phenyl)methylene-S-methyl-thiosemicarbazidato-Fe(III) was determined by X-ray diffraction. A five-coordinate, distorted square-pyramidal geometry was established crystallographically for the iron(III) complex. Cytotoxicity and proliferation properties were determined using human erythromyeloblastoid leukemia and HL-60 mouse promyelocytic leukemia cell lines. For K 562 and HL-60 cells, compounds 1a and 2b were found to be cytotoxic at concentrations of 10 and 20 µg mL^?1.     

Spectrophotometric study of etodolac complexes with copper (II) and iron (III)

A rapid, simple, and selective method was developed for the determination of etodolac. The method depends on complexation of etodolac with copper (II) acetate and iron (III) chloride followed by extraction of complexes with dichloromethane and then measuring the extracted complexes spectrophotometrically at 684 and 385 nm in case of Cu (II) or Fe (III), respectively. Different factors affecting the reaction, such as pH, reagent concentration, and time, were studied. By use of Job's method of continuous variation, the molar ratio method, and elemental analysis, the stoichiometry of the reaction was found to be in the ratio of 1:2 and 1:3, metal:drug in the case of Cu (II) and Fe (III), respectively. The method obeys Beer's law in a concentration range of 2.00-9.00 and 0.50-2.00 mg/mL in case of Cu (II) and Fe (III), respectively. The stability of the complexes formed was also studied, and the reaction products were isolated for further investigation. The complexes have apparent molar absorptivities of about 32.14 +/- 0.97 and 168.32 +/- 1.12 for Cu (II) and Fe (III), respectively. The suggested procedures were successfully applied to the analysis of pure etodolac and its pharmaceutical formulations. The validity of the procedures was further ascertained by the method of standard additions, and the results were compared with other reported spectrophotometric methods and showed no significant difference in accuracy and precision.     

Iron(III), cobalt(II,III), copper(II) and zinc(II) complexes of 2-pyridineformamide 3-piperidylthiosemicarbazone

Reduction of 2-cyanopyridine by sodium in the presence of 3-piperidylthiosemicarbazide produces 2-pyridineformamide 3-piperidylthiosemicarbazone, HAmpip. Complexes with iron(III), cobalt(II,III) copper(II) and zinc(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. In addition, the crystal structures of HAmpip, [Fe(Ampip)₂]ClO₄, [Cu(HAmpip)Cl₂]·CH₃OH and [Zn(HAmpip)Br₂]·C₂H₆SO have been determined. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur when coordinating as the anionic or neutral ligand, respectively.     

Monomeric iron(II) hydroxo and iron(III) dihydroxo complexes stabilized by intermolecular hydrogen bonding

Using the multidentate ligand bis(N-methylimidazol-2-yl)-3-methylthiopropanol (L), the mononuclear iron(II) hydroxo and iron(III) dihydroxo complexes [Fe(II)(L)2(OH)](BF4) (1) and [Fe(III)(L)2(OH)2](BF4) (2) have been synthesized and characterized by X-ray diffraction and spectroscopic methods. The X-ray data suggest that the remarkable stability of the Fe-OH bond(s) in both compounds results from intermolecular hydrogen-bonding interactions between the hydroxo ligand(s) and the tertiary hydroxyl of the L ligands, which prevent further intermolecular reactions.     

Synthesis and characterisation of complexes of iron(II,III), cobalt(II,III) and nickel(II) with dinitrosoresorcinol

Summary Complexes of Fe^II, Fe^III, Co^II, Co^III and Ni^II with dinitroso resercinol (DNR) have been isolated and characterised. Ni studies showed that the metals are coordinated to the oxygens of one hydroxyl and one nitroso group, the second hydroxyl and nitroso groups remaining uncoordinated. The magnetic moments of the Fe^II and Ni^II complexes are commensurate with tetrahedral (or disorted octahedral) structures, while the others are ocahedral, however, the electronic spectra suggest ocahedral stereochemistries for all the complexes.     

Cobalt(II) and iron(III) complexes with 2-substituted benzimidazole derivatives

Summary FeCl₃ and the primary amines 2-aminobenzimidazole (abi) and 2(2-aminophenyl)benzimidazole (apbi) give complexes for which spectroscopic and magnetic data suggest a pentacoordinate [FeCl₄].The reactions of complexes of primary amines of CoCl₂ and FeCl₃ with the carbonyl compounds acetylacetone (Hacac) and pyridylcarbaldehyde (pyc) yield complexes which contain the Schiff bases from the condensation of the amines and the carbonyl groups.Analytical data indicate formulae [CoCl₂(abiacac)₂], [CoCl₂(abipyc)], [FeCl₃(abiacac)], [FeCl₃(abipyc)₂] and [FeCl₃(apbipyc)] for the complexes. The cobalt(II) complexes are pseudo-tetrahedral, while the iron complexes are tetra-, penta-, or hexa-coordinate, as deduced from spectroscopic and magnetic measurements.     

Intervalence electron transfer spectra of several iron(III) and copper(II) pentacyanoferrate(II) complexes

The intervalence spectra of several iron(III) and copper(II) pentacyanoferrate(II) complexes have been studied in comparison to those of the hexacyanoferrate(II) analogs. The energies of the intervalence transitions have shown to be strongly dependent on the properties of the Fe(CN)₅Lⁿ⁻ anion. The observed trend on the energies of the intervalence bands in the sequence NH₃ < py < pyrazinecarboxylate < dimethyl sulfoxide ∼ tetramethylene sulfoxide < CO, for the ligand L, were interpreted in terms of backbonding stabilization of the low spin, iron(II) donor ion.     

O-Tolyldithiocarbonate Complexes of Iron(II) and Iron(III)

Abstract

Reactions of O-tolyldithiocarbonate ligands, (o-, m-, and p-CH₃C₆H₄O)CS₂Na, with anhydrous FeCl₂ (1:2 molar ratio) and with FeCl₃ (1:1 and 1:3 molar ratio) yielded the complexes [{(CreO)CS₂}₂Fe] and [{(CreO)CS₂}_nFeCl_3–n] (Cre = o-, m-, and p-CH₃C₆H₄; n = 1 and 3), respectively. These complexes were reacted with nitrogen and phosphorus donor ligands in dichloromethane, which afforded the adducts corresponded to [{(CreO)CS₂}₂Fe.xL] and [(CreO)CS₂FeCl₂.xL] {x = 1, L = N₂C₁₂H₈; x = 2, L = NC₅H₅, P(C₆H₅)₃}. Elemental analyses and IR, UV-visible, and mass spectroscopic and magnetic studies indicated bidentate mode of bonding by dithiocarbonate ligands leading to sixcoordination around the iron atom as a consequence of Fe…Fe interaction in the complexes [{(CreO)CS₂}₂Fe] and [(CreO)CS₂FeCl₂]. The complexes exhibited antifungal activity. The fungicidal activity of the complexes has been tested by poisoned food technique using fungi Fusarium sp.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental resource: Antifungal Activity.     

Thermal studies on oxalate complexes. II. Complexes of iron (III) and chromium (III)

The decomposition of solid K₃[Fe(C₂O₄)₃] · 2 H₂O and K₃[Cr(C₂O₄)₃] · 3 H₂O has been studied using TGA and DSC. After dehydration, the chromium compound was found to decompose by the loss of CO in two steps, the loss of CO₂ and additional CO, and finally the loss of CO₂. The final product appears to be either K₃CrO₃ or the mixed oxides of chromium and potassium. Kinetic parameters and enthalpy data are presented for these reactions. In the case of K₃[Fe(C₂O₄)₃] · 2 H₂O, dehydration is followed by the loss of CO₂ and CO, CO₂ alone, and finally CO. The final product appears to be a basic carbonate of the type K₃[FE(O)₂(CO₃)]. Kinetic and thermal data are presented for most of these decomposition reactions.