Iron Schiff Base Complexes Research Articles

Iron Complexes Anchored onto Magnetically Separable Graphene Oxide Sheets: An Excellent Catalyst for the Synthesis of Dihydroquinazoline-Based Compounds.

In this work, a green, sustainable, and efficient protocol for the syntheses of dihydroquinazoline derivatives is proposed. Initially, three Schiff base complexes of iron containing the ligand (2,2-dimethylpropane-1,3-diyl)bis(azanylylidene)bis(methanylylidene)bis(2,4-Xphenol), where X = Cl (complex 1)/Br (complex 2)/I (complex 3), were synthesized, fully characterized, and used in the desired syntheses. Complex 1 excelled as a catalyst, closely followed by complexes 2 and 3. DFT calculations helped in rationalizing the role of the halide substituent in the ligand backbone as a relevant factor in the catalytic superiority of complex 1 over complexes 2 and 3 for the synthesis of the dihydroquinazoline derivatives. Finally, to facilitate catalyst recoverability and reusability, complex 1 was immobilized on GO@Fe3O4@APTES (GO, graphene oxide; APTES, 3-aminopropyltriethoxysilane) to generate GO@Fe3O4@APTES@FeL1 (GOTESFe). GOTESFe was thoroughly characterized through scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy and efficiently used for the synthesis of dihydroquinazoline derivatives. GOTESFe could be magnetically recovered and reused up to five cycles without compromising its catalytic efficiency. Therefore, immobilization of the chosen iron complex onto magnetic GO sheets offers an extremely competent route in providing a blueprint of a readily recoverable, reusable, robust, and potent catalyst for the synthesis of dihydroquinazoline-based compounds.

Non‐Macrocyclic Schiff Base Complexes of Iron(II) as ParaCEST Agents for MRI

Nearly two decades of research efforts have been devoted to paramagnetic chemical exchange saturation transfer (paraCEST) to produce image contrast in magnetic resonance imaging. Less than twenty iron‐based paraCEST agents have been reported so far, the majority of which are ligated by macrocyclic chelates. In the work presented here three isostructural tripodal ligands sharing a common tris‐(aza‐butenyl)amine foundation are explored to further diversify iron‐based paraCEST agents. One of the complexes provides contrast with a CEST effect of 33 % for a 10 mm sample, a paramagnetic shift (Δω) of 85 ppm from bulk H2O, and exhibits some stability to biologically relevant ions.

Electrocatalytic Reduction of CO2 to Formate by an Iron Schiff Base Complex.

The synthesis, structural characterization, and reactivity of an iron(III) chloride compound of 6,6'-di(3,5-di-tert-butyl-2-hydroxybenzene)-2,2'-bipyridine (Fe(tbudhbpy)Cl), under electrochemically reducing conditions is reported. In the presence of carbon dioxide (CO2) under anhydrous conditions in N,N-dimethylformamide (DMF), this complex mediates the 2e- reductive disproportionation of two equivalents of CO2 to carbon monoxide (CO) and carbonate (CO32-). Upon addition of phenol (PhOH) as a proton source under CO2 saturation, catalytic current is observed; product analysis from controlled potential electrolysis experiments shows the majority product is formate (68 ± 4% Faradaic efficiency), with H2 as a minor product (30 ± 10% Faradaic efficiency) and minimal CO (1.1 ± 0.3% Faradaic efficiency). On the basis of data obtained from cyclic voltammetry and infrared spectroelectrochemistry (IR-SEC), the release of CO from intermediate Fe carbonyl species is extremely slow and undergoes competitive degradation, limiting the activity and lifetime of this catalyst. Mechanistic studies also indicate the phenolate moieties coordinated to Fe are sensitive to protonation in the reduced state, suggesting the possibility of cooperative pendent proton interactions being involved in CO2 reduction.

Base metal Schiff base complexes applied as catalysts for the oxidation of n-octane

The catalytic oxidation of n-octane to value-added oxygenates has been studied with a series of salen-type complexes of iron. The four iron Schiff base complexes N,N′-bis(salicylidene)-L-iron(III) chloride [L=1,2-phenylenediamine (5); ethylenediamine (6); propylenediamine (7) and butylenediamine (8)] were synthesised by variation of the bridging diamine backbone. All the complexes are fully characterised and the crystal structure of 7 is for the first time reported as a centrosymmetric dimer observed to crystallise in the triclinic P1‾ system. The application of 5–8 in this oxidation reaction represents a rare example of the systematic use of iron-salen complexes for the liquid-phase functionalisation of Csp3–H bonds of straight chain alkanes. All catalysts displayed activity with H2O2 and TBHP as oxidants that resulted in a mixture of oxygenated products dominated by the ketones (2-, 3- and 4-octanones). Observed trends and variations in catalytic activities of the complexes is related to differences in chemical/structural features and changes in reaction conditions. A detailed analysis of selectivity parameters of the complexes to the variety of oxygenates is also presented and rationalised.

Synthesis and structural studies of polymer-supported transition metal complexes: Efficient catalysts for oxidation of phenol

In this work, a new simple and reproducible method for preparation of a series of novel recyclable complexes is described. The series includes unsupported 3-MHBdMBn–Met complexes (Met = iron(III), cobalt(II), nickel(II), copper(II) and zinc(II) ions), and polystyrene anchored (P-3-MHBdMBn–Met) metal ion complexes, supported by—ONNO-tetradentate Schiff-base ligand. These free and polymer anchored metal complexes are prepared by the reactions of metal solution with one molar equivalent of unsupported 3-MHBdMBn (N,N'-bis(2-hydroxy-3-methylbenzaldehyde)-4-methylbenzene-1,2-diamine) or polymer-supported (P-3-MHBdMBn) Schiff-base ligands in methanol under nitrogen atmosphere. The greatest advantage of this catalyst system over other polymer-supported catalysts is a remarkably low cost and the quality of being recycled up to six times. These benefits are due to the easily accessible materials and the simple synthetic route. A higher efficiency of complexation of metal ions on the polymer anchored 3-MHBdMBn Schiff base compared to that shown by an unsupported analogue is another advantages of this catalyst system. The structural study reveals that iron(III) complex is octahedral in geometry, whereas cobalt(Il), nickel(II) and copper(II) complexes are square planar and zinc(II) complex is of tetrahedral geometry. The catalytic activities of polystyrene-supported metal complexes toward the oxidation of phenol are investigated. Experimental results indicate that the reactivity of P-3-MHBdMBn–Met is dramatically affected by the polymer support and iron complexes are more active than other complexes. The rate of phenol conversion is high (2.41 × 10–6 mol dm–3 s–1) in the presence of polystyrene-supported 3-MHBdMBn Schiff base complexes of iron(III) ions and low in the presence of zinc(II) analogue (1.36 × 10–6 mol dm–3 s–1).

Degradation of organic pollutants in waters by a water-insoluble iron(III) Schiff base complex

To degrade organic pollutants in water with hydrogen peroxide (H2O2) under visible light (λ≥420nm), a novel water-insoluble iron Schiff base complex, iron(III)-bis-salicylaldehyde-o-aminophenol (Fe-SAP), was prepared and characterized using NMR, MS, IR, and UV–Vis spectroscopy. Rhodamine B (RhB) and salicylic acid were used as probes to characterize the photocatalytic system. High catalytic activity of Fe-SAP was observed over a wide range of pH values from 3 to 9. Scavenging studies of reactive oxygen species (ROS) and ESR experiments indicate that the primary ROS from photocatalytic conversion of H2O2 is 1O2, rather than OH. To date, there have been few reports on the generation of 1O2 by iron organic complexes for the oxidative decomposition of organics. The catalyst stability and reusability are good, most likely because the water-insoluble Fe-SAP is able to reduce the damage to its organic ligands by OH. Given these favorable characteristics, Fe-SAP exhibits excellent potential for practical application in removing refractory organic pollutants and pollutants of emerging concern from water and wastewater.

An iron Schiff base complex loaded mesoporous silica nanoreactor as a catalyst for the synthesis of pyrazine-based heterocycles

An iron Schiff base complex was encapsulated in SBA-15 mesoporous silica to afford a Fe(III)-Schiff base/SBA-15 heterogeneous nanocatalyst for the synthesis of pyridopyrazine and quinoxaline heterocycles. These reactions proceeded in water with excellent yields. The catalyst was characterized by physico-chemical and spectroscopic methods and found to retain the characteristic channel structures of the SBA-15, allowing good accessibility of the encapsulated metal complex.

Comprehensive Study on the Binding of Iron Schiff Base Complex with DNA and Determining the Binding Mode

The iron (III) [N, N' Bis (5-(triphenyl phosphonium methyl) salicylidene)-1, 2 ethanediamine] chloride [Fe Salen]Cl, has been synthesized and characterized as described previously. The interaction of iron complex with calf thymus (CT) DNA has been studied extensively by experimental techniques. Absorption spectra showed both hypochromism and hyperchromism. Thermal denaturation study of DNA with complex revealed the ΔTm of 5°C. Competitive binding study shows that the enhanced emission intensity of ethidium bromide (EB) in the presence of DNA was quenched by adding of the iron complex indicating that it displaces EB from its binding site in DNA and the apparent binding constant has been estimated to be 5 × 10(6) μM(-1). Fluorescence Scatchard plot revealed type B behavior for interaction of complex to DNA. Circular dichroism (CD) spectra measurements showed that the complex interacts with DNA via surface and groove bindings. Linear dichroism (LD) measurements confirmed the bending of DNA in the presence of complex. Furthermore, Isothermal titration calorimetry (ITC) experiments approved that the binding of complex is based on both electrostatic and hydrophobic interactions. More, ITC profile exhibits the existence of two binding phases for the complex.

Sulfur-Containing Schiff Base Complexes of Iron(III) and Lead(II): Synthesis, Characterization, Antimicrobial Activity, and Their Electrochemical Behaviors

The sulfur–nitrogen donor ligands, thiosemicarbazones of 5-nitro-1H-indole-2,3-dione and 6-nitro-1H-indole-2,3-dione and 5-chloro-1H-indole-2,3-dione, have been prepared by the condensation of thiosemicarbazide with respective ketones in 1:1 molar ratio in ethanol medium. Lead and iron complexes were prepared by the reaction of lead(II) chloride and iron(III) chloride with the ligands in a 1:2 molar ratio, respectively. The newly synthesized complexes have been characterized by elemental analysis, melting point determinations, and UV, ESR, and IR spectral studies. In all the complexes, the monobasic bidentate nature of the ligand is evident. Based on analytical and spectral data, hexacoordinated structure for lead and pentacoordinated structure for iron complexes have been proposed. Antibacterial and antifungal studies of these compounds against various pathogenic bacterial and fungal strains have been carried out. One of the ligands and its metal complexes were screened for their antifertility activity. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Synthesis of polymer‐supported metal‐ion complexes and evaluation of their catalytic activities

AbstractPolymer‐supported transition‐metal‐ion complexes of the N,N′‐bis(o‐hydroxy acetophenone) propylenediamine (HPPn) Schiff base were prepared by the complexation of iron(III), cobalt(II), and nickel(II) ions on a polymer‐anchored N,N′‐bis(5‐amino‐o‐hydroxy acetophenone) propylenediamine Schiff base. The complexation of iron(III), cobalt(II), and nickel(II) ions on the polymer‐anchored HPPn Schiff base was 83.44, 82.92, and 89.58 wt%, respectively, whereas the unsupported HPPn Schiff base showed 82.29, 81.18, and 87.29 wt % complexation of these metal ions. The iron(III) ion complexes of the HPPn Schiff base showed octahedral geometry, whereas the cobalt(II) and nickel(II) ion complexes were square planar in shape, as suggested by spectral and magnetic measurements. The thermal stability of the HPPn Schiff base increased with the complexation of metal ions, as evidenced by thermogravimetric analysis. The HPPn Schiff base showed a weight loss of 51.0 wt % at 500°C, but its iron(III), cobalt(II), and nickel(II) ion complexes showed weight losses of 27.0, 35.0, and 44.7 wt % at the same temperature. The catalytic activity of the unsupported and supported metal‐ion complexes was analyzed by the study of the oxidation of phenol and epoxidation of cyclohexene in the presence of hydrogen peroxide. The supported HPPn Schiff base complexes of iron(III) ions showed a 73.0 wt % maximum conversion of phenol and 90.6 wt % epoxidation of cyclohexene, but unsupported complexes of iron(III) ions showed 63.8 wt % conversion of phenol and 83.2 wt % epoxidation of cyclohexene. The product selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was 93.1 wt % and 98.1 wt % with the supported HPPn Schiff base complexes of iron(III) ions, but it was low with the supported Schiff base complexes of cobalt(II) and nickel(II) ions. The selectivity for CTL and ECH varied with the molar ratio of the metal ions but remained unaffected by the molar ratio of hydrogen peroxide to the substrate. The energy of activation for the epoxidation of cyclohexene and oxidation of phenol with the polymer‐supported Schiff base complexes of iron(III) ions was 10.0 and 12.7 kJ/mol, respectively, but it was found to be higher with the supported HPPn Schiff base complexes of cobalt(II) and nickel(II) ions and with the unsupported HPPn Schiff base complexes of iron(III), cobalt(II), and nickel(II) ions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci 2008

Catalytic activities of polymer‐supported metal complexes in oxidation of phenol and epoxidation of cyclohexene

AbstractThe metal complexes of N, N′‐bis (o‐hydroxy acetophenone) propylene diamine (HPPn) Schiff base were supported on cross‐linked polystyrene beads. The complexation of iron(III), copper(II), and zinc(II) ions on polymer‐anchored HPPn Schiff base was 83.4, 85.7, and 84.5 wt%, respectively, whereas the complexation of these metal ions on unsupported HPPn Schiff base was 82.3, 84.5, and 83.9 wt%. The iron(III) complexes of HPPn Schiff base were octahedral in geometry, whereas copper(II) and zinc(II) ions complexes were square planar and tetrahedral. Complexation of metal ions increased the thermal stability of HPPn Schiff base. Catalytic activity of metal complexes was tested by studying the oxidation of phenol and epoxidation of cyclohexene in the presence of hydrogen peroxide. The polymer‐supported HPPn Schiff base complexes of iron(III) ions showed 73.0 wt% conversion of phenol and 90.6 wt% conversion of cyclohexene at a molar ratio of 1:1:1 of substrate to catalyst and hydrogen peroxide, but unsupported complexes of iron(III) ions showed 63.8 wt% conversion for phenol and 83.2 wt% conversion for cyclohexene. The product selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was 93.1 and 98.3 wt%, respectively with supported HPPn Schiff base complexes of iron(III) ions but was lower with HPPn Schiff base complexes of copper(II) and zinc(II) ions. Activation energy for the epoxidation of cyclohexene and phenol conversion with unsupported HPPn Schiff base complexes of iron(III) ions was 16.6 kJ mol−1 and 21.2 kJ mol−1, respectively, but was lower with supported complexes of iron(III) ions. Copyright © 2007 John Wiley & Sons, Ltd.

Polymer Supported Schiff Base Complexes of Iron(III), Cobalt(II) and Nickel(II) Ions and their Catalytic Activity in Oxidation of Phenol and Cyclohexene

The polymer supported transition metal complexes of N,N′‐bis (o‐hydroxy acetophenone) hydrazine (HPHZ) Schiff base were prepared by immobilization of N,N′‐bis(4‐amino‐o‐hydroxyacetophenone)hydrazine (AHPHZ) Schiff base on chloromethylated polystyrene beads of a constant degree of crosslinking and then loading iron(III), cobalt(II) and nickel(II) ions in methanol. The complexation of polymer anchored HPHZ Schiff base with iron(III), cobalt(II) and nickel(II) ions was 83.30%, 84.20% and 87.80%, respectively, whereas with unsupported HPHZ Schiff base, the complexation of these metal ions was 80.3%, 79.90% and 85.63%. The unsupported and polymer supported metal complexes were characterized for their structures using I.R, UV and elemental analysis. The iron(III) complexes of HPHZ Schiff base were octahedral in geometry, whereas cobalt(II) and nickel(II) complexes showed square planar structures as supported by UV and magnetic measurements. The thermogravimetric analysis (TGA) of HPHZ Schiff base and its metal complexes was used to analyze the variation in thermal stability of HPHZ Schiff base on complexation with metal ions. The HPHZ Schiff base showed a weight loss of 58% at 500°C, but its iron(III), cobalt(II) and nickel(II) ions complexes have shown a weight loss of 30%, 52% and 45% at same temperature. The catalytic activity of metal complexes was tested by studying the oxidation of phenol and epoxidation of cyclohexene in presence of hydrogen peroxide as an oxidant. The supported HPHZ Schiff base complexes of iron(III) ions showed 64.0% conversion for phenol and 81.3% conversion for cyclohexene at a molar ratio of 1∶1∶1 of substrate to catalyst and hydrogen peroxide, but unsupported complexes of iron(III) ions showed 55.5% conversion for phenol and 66.4% conversion for cyclohexene at 1∶1∶1 molar ratio of substrate to catalyst and hydrogen peroxide. The product selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was 90.5% and 96.5% with supported HPHZ Schiff base complexes of iron(III) ions, but was found to be low with cobalt(II) and nickel(II) ions complexes of Schiff base. The selectivity for catechol (CTL) and epoxy cyclohexane (ECH) was different with studied metal ions and varied with molar ratio of metal ions in the reaction mixture. The selectivity was constant on varying the molar ratio of hydrogen peroxide and substrate. The energy of activation for epoxidation of cyclohexene and phenol conversion in presence of polymer supported HPHZ Schiff base complexes of iron(III) ions was 8.9 kJ mol−1 and 22.8 kJ mol−1, respectively, but was high with Schiff base complexes of cobalt(II) and nickel(II) ions and with unsupported Schiff base complexes.

Reaction of Some Schiff Base Complexes of Iron(III) with Nitrogen and Sulfur Donor Anions

Reactions of some Schiff bases with Fe(III) salts in the presence of nitrogen or sulfur donor anions have been investigated. The Schiff bases are derived from the reaction of salicylaldehyde, substituted salicyaldehyde or 2-hydroxy-1 -naphthaldehyde with 8-aminoquinoline, substituted aniline, ethylenediamine or o-phenylenediamine. The obtained Schiff bases act either as tridentate or tetradentate dibasic ligands. Tentative structures have been assigned on the basis of elemental analyses, conductivity, spectral and magnetic data. Most of the obtained complexes are proposed to be hexa-coordinate but some might be penta-coordinate. The added anions (thiocynate, 8-aminoquinolate, pyrrolidinedithiocarbamate or piperazinedi(dithiocarbamate) are bonded to iron, in addition to the Schiff base, producing mononuclear complexes or act as bridging groups producing dinuclear or polynuclear complexes.

ChemInform Abstract: ACTIVATION VOLUMES FOR HYDROXIDE ATTACK AT SCHIFF BASE COMPLEXES OF IRON(II) IN METHANOL‐, TERT‐BUTYL ALCOHOL‐, AND DIMETHYL SULFOXIDE‐WATER SOLVENT MIXTURES

Chemischer InformationsdienstVolume 15, Issue 26 Organoelement Compounds ChemInform Abstract: ACTIVATION VOLUMES FOR HYDROXIDE ATTACK AT SCHIFF BASE COMPLEXES OF IRON(II) IN METHANOL-, TERT-BUTYL ALCOHOL-, AND DIMETHYL SULFOXIDE-WATER SOLVENT MIXTURES J. BURGESS, J. BURGESSSearch for more papers by this authorC. D. HUBBARD, C. D. HUBBARDSearch for more papers by this author J. BURGESS, J. BURGESSSearch for more papers by this authorC. D. HUBBARD, C. D. HUBBARDSearch for more papers by this author First published: June 26, 1984 https://doi.org/10.1002/chin.198426301AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume15, Issue26June 26, 1984 RelatedInformation

Activation volumes for hydroxide attack at Schiff base complexes of iron(II) in methanol-, tert-butyl alcohol-, and dimethyl sulfoxide-water solvent mixtures

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTActivation volumes for hydroxide attack at Schiff base complexes of iron(II) in methanol-, tert-butyl alcohol-, and dimethyl sulfoxide-water solvent mixturesJohn Burgess and Colin D. HubbardCite this: J. Am. Chem. Soc. 1984, 106, 6, 1717–1721Publication Date (Print):March 1, 1984Publication History Published online1 May 2002Published inissue 1 March 1984https://doi.org/10.1021/ja00318a027RIGHTS & PERMISSIONSArticle Views95Altmetric-Citations25LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (648 KB) Get e-Alerts Get e-Alerts

Kinetics of reactions of Schiff-base complexes of iron(II). Part 6. The preparation and kinetics of reactions of complexes of multidentate ligands

Preparations of iron(II) complexes of bi-, tri-, quadri-, quinque-, and sexi-dentate Schiff bases are reported. The Schiff-base ligands are derived from pyridine-2-carbaldehyde, phenyl 2-pyridyl ketone, pyridine-2,6-dicarb-aldehyde. or 2,6-diacetylpyridine, and appropriate amines. All these complexes aquate in acid solution, and react with cyanide to give ternary iron(II)–cyanide–Schiff-base complexes. The kinetics of aquation of several of these Schiff-base complexes, and the kinetics of cyanide attack at all the complexes, are described, and reactivities are compared with those for analogous reactions of other iron(II) di-imine complexes. Solvent effects on the re-activity with cyanide of one of the complexes of the sexidentate Schiff bases in a range of binary aqueous mixtures are discussed.

Kinetics of reactions of Schiff base complexes of iron(II). V. Reactions of the complex of the hexadentate ligand NN‴‐bis‐[α‐(2‐pyridyl)benzylidene]triethylenetetramine in acid solution and with hydroxide, cyanide, and peroxodisulphate

AbstractThe preparation and characterization of the iron(II) complex of the hexadentate Schiff base ligand NN‴‐bis‐[α‐(2‐pyridyl)benzylidene]triethylenetetramine are reported. Kinetic patterns and rate constants for aquation of this complex, and for its reactions with hydroxide, cyanide, and peroxodisulphate have been determined. Activation parameters for the reaction with cyanide, in aqueous solution, are ΔH‡ = 24.3 kcal/mole and ΔS‡ = +1 cal/deg‐mole.

Kinetics of reactions of Schiff-base complexes of iron(II). Part III. Reactions of tris-[N-(2-pyridylmethylene)aniline] complexes with peroxodisulphate and of tris-[α-(2-pyridyl)benzylideneaniline] complexes with acid, with hydroxide, and with peroxodisulphate

The kinetics of reactions of several substituted tris-[N-(2-pyridylmethylene)aniline]iron(II) complexes with peroxodisulphate in aqueous solution; of tris-[α-(2-pyridyl)benzylideneaniline]iron(II) complexes with acid, hydroxide, and peroxodisulphate in aqueous ethanolic solution; and of bis(maleonitriledithiolato)cobaltate(II) with acid and with peroxodisulphate in aqueous solution are reported. The kinetic behaviour of the tris-[α-(2-pyridyl)-benzylideneaniline]iron(II) complexes in acid and alkaline solution is similar to that of the related tris-(1,10-phenanthroline)iron(II) complex. Reaction of peroxodisulphate with tris-[N-(2-pyridylmethylene)aniline]-iron(II) complexes takes place by parallel ligand dissociation and complex oxidation, whereas reaction of the tris-[α-(2-pyridyl)benzylideneaniline]iron(II) and bis(maleonitriledithiolato)cobaltate(II) complexes is entirely dissociative with no evidence for any direct oxidation of these complexes to the corresponding iron(III) and cobalt(III) compounds.

Kinetics of reactions of Schiff base complexes of iron(II). Part II. Reactions of substituted tris-[N-(2-pyridylmethylene)aniline]complexes with bases and with hydrogen peroxide

Kinetics of reactions of substituted tris-[N-(2-pyridylmethylene)aniline]iron(II) complexes with hydrogen peroxide, with 2,2′-bipyridyl and related compounds, and with hydroxide ion are reported. Reaction with hydrogen peroxide proceeds by rate-determining loss of one ligand molecule, as in acid fission, followed by rapid reaction of intermediates with hydrogen peroxide. Reaction with 2,2′-bipyridyl also proceeds by rate-determining loss of one ligand molecule followed by complete conversion into the tris-(2,2′-bipyridyl)iron(II) complex. Reaction with hydroxide ion occurs partly by dissociation and partly by direct nucleophilic attack. Correlation of substituent effects on the rates for hydroxide attack with Hammett σ-values is described. Finally, reactions of nitro- and related substituent complexes, which behave anomalously in acid fission, are discussed.