Iron Diimine Research Articles

1,4-Selective Hydrovinylation of Diene Catalyzed by an Iron Diimine Catalyst: A Computational Case Study on Two-State Reactivity

First-row transition-metal catalysis has been attracting great attention in recent years, partly due to its low toxicity and low cost, as well as a wide variety in reactivities. However, the theore...

Selective [1,4]-Hydrovinylation of 1,3-Dienes with Unactivated Olefins Enabled by Iron Diimine Catalysts.

The selective, intermolecular [1,4]-hydrovinylation of conjugated dienes with unactivated α-olefins catalyzed by α-diimine iron complexes is described. Value-added "skipped" diene products were obtained with exclusive [1,4]-selectivity, and the formation of branched, ( Z)-olefin products was observed with no evidence for alkene isomerization. Mechanistic studies conducted with the well-defined, single-component iron precatalyst (MesDI)Fe(COD) (MesDI = [2,4,6-Me3-C6H2-N═CMe]2); COD = 1,5-cyclooctadiene) provided insights into the origin of the high selectivity. An iron diene complex was identified as the catalyst resting state, and one such isoprene complex, (iPrDI)Fe(η4-C5H8), was isolated and characterized. A combination of single crystal X-ray diffraction, Mößbauer spectroscopy, magnetic measurements, and DFT calculations established that the complex is best described as a high-spin Fe(I) center ( SFe = 3/2) engaged in antiferromagnetic coupling to an α-diimine radical anion ( SDI = -1/2), giving rise to the observed S = 1 ground state. Deuterium-labeling experiments and kinetic analyses of the catalytic reaction provided support for a pathway involving oxidative cyclization of an alkene with the diene complex to generate an iron metallacycle. The observed selectivity can be understood in terms of competing steric interactions in the transition states for oxidative cyclization and subsequent β-hydrogen elimination.

Spin transitions in bis(amidinato)-N-heterocyclic carbene iron(II) and iron(III) complexes.

In contrast to high spin pyridyl diimine iron(ii) dichloride complexes, analogous bis(amidinato)-N-heterocyclic carbene iron(ii) and iron(iii) complexes demonstrate complex magnetic behaviour. In the solid state, they are best described as intermediate spin complexes at low temperatures that demonstrate gradual spin transitions beginning near or below room temperature. Treating the bis(amidinato)-N-heterocyclic carbene iron(ii) complex with an aryl azide revealed enhanced reactivity compared to analogous complexes supported by pyridyl diimine ligands.

Micron‐granula polyolefin with self‐immobilized nickel and iron diimine catalysts bearing one or two allyl groups

AbstractSelf‐immobilized nickel and iron diimine catalysts bearing one or two allyl groups of [ArNC]2(C10H6)NiBr2 [Ar = 4‐allyl‐2,6‐(i‐Pr)2C6H2] (1), [ArNC(Me)][Ar′N C(Me)]C5H3NFeCl2 [Ar = Ar′ = 4‐allyl‐2,6‐(i‐Pr)2C6H3, Ar = 2,6‐(i‐Pr)2C6H3, and Ar′ = 4‐allyl‐2,6‐(i‐Pr)2C6H3] were synthesized and characterized. All three catalysts were investigated for olefin polymerization. As a result, these catalysts not only showed high activities as the catalyst free from the allyl group, such as [ArNC]2C10H6NiBr2 (Ar = 2,6‐(i‐Pr)2C6H2)], but also greatly improved the morphology of polymer particles to afford micron‐granula polyolefin. The self‐immobilization of catalysts, the formation mechanism of microspherical polymer, and the influence on the size of the particles are discussed. The molecular structure of self‐immobilized nickel catalyst 1 was also characterized by crystallographic analysis. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1018–1024, 2004

Ethylene oligomerization by diimine iron(II) complexes/EAO

The catalytic properties of a series of Fe(II) diimine complexes (diimine= N, N′- o-phenylenebis(salicylideneaminato), N, N′-ethylenebis(salicylideneaminato), N, N′- o-phenylenebisbenzal, N, N′-ethylenebisbenzal) in combination with ethylaluminoxane (EAO) for ethylene oligomerization have been investigated. Treatment of the iron(II) complexes with EAO in toluene generates active catalytic systems in situ that oligomerize ethylene to low-carbon olefins. The effects of reaction temperature, ratios of Al/Fe and reaction periods on catalytic activity and product distribution have been studied. The activity of complex FeCl 2(PhCH o-NC 6H 4NCHPh) with EAO at 200°C is 1.35×10 5 g oligomers/mol Fe·h, and the selectivity of C 4–10 olefins is 84.8%.

Iron–diimine–cyanide complexes as probes for aqueous micellar systems

Medium effects on the charge-transfer bands of solvatochromic iron–diimine–cyanide complexes in aqueous micellar systems are described. The observed shifts in max for these bands are discussed in terms of the charges on both the complexes and the surfactants, and in relation to the critical micellar concentrations.

Volumes of activation for dissociation of the cations of [tris-2,2′-bipyridyl]iron(II), [tris-1,10- phenanthroline]iron(II) and of other diimine iron(II) complexes in aqueous solution

The kinetics of dissociation of several iron(II) diimine complexes by aqueous hydroxide ions have been studied spectrophotometrically at atmospheric pressure and elevated pressures, at 298.2 K. Values of Δ V * are between + 10 and + 16 cm 3 mol −1, and are interpreted as arising from a significant loss of electrostricted water from the hydroxide ion as it reacts with the iron(II) complex associatively. Dissociation of the [Fe(5NO 2phen) 3] 2+ and [Fe(5Brphen) 3] 2+ complexes in the presence of aqueous EDTA is reported. For both, Δ V * is + 22 cm 3 mol −1. These values can be understood by considering the reaction as a process comparable to aquation in acidic medium, a dissociative process. Activation enthalpy data support this idea.

Counterion micellar effects upon the reaction of low-spin diimine iron(II) complexes

The rate of reaction of tris(1,10-phenanthroline)iron(II) ion (1a), tris(3,4,7,8-tetramethyl-1,10-phenanthroline)iron(II) ion (1b), and tris(4,7-diphenhyl-1, 10-phenanthroline)iron(II) ion (1c) with hydroxide ion, in cationic micelles, is strongly affected by the concentration of micellar counterion in solution. The reaction of la in CTACl is modestly speeded up by the addition of added KCl, while the reactions of 1b and 1c are strongly inhibited by the addition of large amounts of KCl and KBr to micellar solutions of CTACl and CTABr, respectively. These rate effects fit the pseudophase-ion exchange model, assuming the binding of the substrates to the micelles depends upon the counterion concentration. Keywords: counterion micellar effects, low-spin diimine iron(II) complexes.

Low valence states of iron complexes of aliphatic and mixed aliphatic-aromatic diimine ligands

Electrochemical reductions of iron(II) diimine complexes [FeL 3 2+, where L = CH 3NC(R)C(R′) NCH 3, aliphatic diimine series with R,R′ = H,H; H,CH 3 and CH 3,CH 3 and L = C 5H 4NC(R)N(R′), mixed diimine series with R,R′ = H,CH 3 and CH 3] were investigated through polarography and cyclic voltammetry in acetonitrile, with tetraethylammonium perchlorate supporting electrolyte (0.2 M) as a function of temperature. In the 0 to −2.4 V vs. Ag/AgCl potential range two to four polarographic waves were observed for the aliphatic series. The first two waves can be described as one-electron reversible reduction processes. They indicate that low valence states iron(I) and iron(0) are stabilized in acetonitrile. In the mixed ligand series three one-electron reversible reduction waves were observed, indicating that in addition to the low valence states stabilized in the aliphatic diimine series the formal reduction state Fe(–I) is also stabilized. The stabilization of the low oxidation states is due to the electron acceptor properties of the diimine ligands, inherent to the presence of the chromophoric iron diimine group. The half-wave potential data and the stabilization of the low valence states point to the importance of analyzing both σ and π effects. The molecular electronegativity values for the series of iron diimine complexes investigated evidences a synergistic interaction between the metal-ligand σ and π bonds. Diffusion coefficients, temperature effects on the heterogeneous electron transfer step, and electrocapillary curves were obtained for these complexes. No evidence for adsorption of the complexes on mercury electrodes was found for the one-electron reversible steps. When comparing polarographic data with those obtained on platinum disk working electrodes employed in the cyclic voltammetric experiments, we observed that for the symmetric aliphatic diimine ligands the observed cathodic currents are larger than expected on the basis of the previously calculated diffusion coefficients. In addition, the reduction waves are shifted 0.14 V to more negative potentials. The symmetric aliphatic diimine complexes exhibit adsorption of the electroactive species on the surface of the platinum electrodes in this potential range.

ChemInform Abstract: LIGAND‐OXIDATION IN IRON DIIMINE COMPLEXES. VI. THE IMPORTANCE OF SOLVATION ON LIGAND‐REACTIVITY

Chemischer InformationsdienstVolume 13, Issue 8 Organoelement Compounds ChemInform Abstract: LIGAND-OXIDATION IN IRON DIIMINE COMPLEXES. VI. THE IMPORTANCE OF SOLVATION ON LIGAND-REACTIVITY H. L. CHUM, H. L. CHUMSearch for more papers by this authorM. ROCK, M. ROCKSearch for more papers by this authorT. RABOCKAI, T. RABOCKAISearch for more papers by this author H. L. CHUM, H. L. CHUMSearch for more papers by this authorM. ROCK, M. ROCKSearch for more papers by this authorT. RABOCKAI, T. RABOCKAISearch for more papers by this author First published: February 23, 1982 https://doi.org/10.1002/chin.198208316Read the full textAboutPDF 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 onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume13, Issue8February 23, 1982 RelatedInformation

Substituent effects on iron diimine complexes. Part 3. Correlations with thermodynamic and spectral properties in a 25.degree.C molten salt

Substituent effects on iron diimine complexes. Part 3. Correlations with thermodynamic and spectral properties in a 25.degree.C molten salt

ChemInform Abstract: LIGAND OXIDATION IN IRON DIIMINE COMPLEXES. 4. TEMPERATURE AND ACIDITY DEPENDENCE OF THE OXIDATION OF TRIS(GLYOXAL BIS(METHYLIMINE))IRON(II) BY CERIUM(IV)

Chemischer InformationsdienstVolume 11, Issue 28 Organoelement Compounds ChemInform Abstract: LIGAND OXIDATION IN IRON DIIMINE COMPLEXES. 4. TEMPERATURE AND ACIDITY DEPENDENCE OF THE OXIDATION OF TRIS(GLYOXAL BIS(METHYLIMINE))IRON(II) BY CERIUM(IV) H. L. CHUM, H. L. CHUMSearch for more papers by this authorM. E. M. HELENE, M. E. M. HELENESearch for more papers by this author H. L. CHUM, H. L. CHUMSearch for more papers by this authorM. E. M. HELENE, M. E. M. HELENESearch for more papers by this author First published: July 15, 1980 https://doi.org/10.1002/chin.198028274Read the full textAboutPDF 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 onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue28July 15, 1980 RelatedInformation

Ligand oxidation in iron diimine complexes. 4. Temperature and acidity dependence of the oxidation of tris(glyoxal bis(methylimine))iron(II) by cerium(IV)

Ligand oxidation in iron diimine complexes. 4. Temperature and acidity dependence of the oxidation of tris(glyoxal bis(methylimine))iron(II) by cerium(IV)

Ligand oxidation in iron diimine complexes. V. Kinetics of the oxidation of tris[2-pyridinal-α-methyl-(methylimine)] iron(II) by cerium(IV)

At low acid concentration, e.g., <4 MH 2SO 4, the cerium(IV) oxidation of the iron(II) complex of the mixed-diimine ligand 2-pyridinal-α-methyl-(methylimine), PMM = C 5H 4NC(CH 3)NCH 3, is a very complex reaction in which ligand-oxidized iron(II) and iron(III) complexes are formed and partly dissociated, with a total consumption of 10–11 equivalents of Ce(IV) per mole of Fe(PMM) 2+ 3. The major oxidation product in ∼50% yield is Fe(PO) 3+ 3, where PO = C 5H 4NC(CHO)NCH 3. The oxisation product has the α-methyl group oxidized to an aldehyde group. At the beginning of the reaction (<25% of the total Ce(IV) comsumption) Fe(PMM) 2Po 2+ was identified as the major reaction product: Ce(IV) + Fe(PMM) 2+ 3 = Ce(III) + Fe(PMM) 3+ 3 → 0.75 Fe- (PMM) 2+ 3 + 0.25 Fe(PMM) 2PO 2+. At this stage the kinetics of the reaction was analyzed by two potentiometric techniques. From experiments of addition of Fe(PMM) 3+ 3, prepared in 5 M H 2SO 4, to Fe(PMM) 2+ 3, to a final 1 M H 2SO 4 concentration, the variation of the potential of the Fe(PMM) 3+ 3/Fe(PMM) 2+ 3 couple is recorded with time. This variation is associated with the rate of disproportionation of Fe(PMM) 3+ 3 yielding Fe(PMM) 2PO 2+ and the original iron(II) complex. the rate law from these experiments is -d[Fe(PMM) 3+ 3]/dt = k[Fe(PMM) 3+ 3] 1.5. From automatic titration experiments, in which CE(IV) is added to Fe(PMM) 2+ 3 solutions at constant rate (ϱ), at high Fe(PMM) 3+ 3 concentration, the rate law is ϱ = k′[Fe(PMM) 3+ 3]. A mechanism, similar to that proposed for the oxidation of the aliphatic diimine complexes, is proposed. The first step is the formation of Fe(PMM) 3+ 3 and Ce(III) with an equilibrium constant of 4.4 × 10 7. The iron(III) complex undergoes an intramolecular reduction to the iron(II) state with concomitant radical formation at the ligand, in a step assisted by solvent water and retarded by acid. Further oxidation of the iron(II) complex-ligand-radical by Fe(PMM) 3+ 3 to the final production of Fe(PMM) 2PO 2+ leads to the derivation on the following rate law, (ϱ) - (d[Fe(PMM) 3+ 3]/dt) = (3k 3K 7[Fe(PMM) 3+ 3] 2)/ (k 4 + k 7 [Fe(PMM) 3+ 3]), which at high [Fe(PMM) 3+ 3] (automatic titrations) reduces to a first order reaction [Fe(PMM) 3+ 3] with k 3 = 0.02 s -1. Analysis of the potential variation experiments with time (low [Fe(PMM) 3+ 3]) with the whole kinetic expression above leads to k 3 = 0.02 s 1-.

Substituent effects on iron diimine complexes II. Correlations with thermodynamic and spectral properties in acetonitrile

The electrochemical oxidation of nineteen iron(II) complexes, FeL 2+ 3, with aliphatic diimine ligands, L = H 3CNC(R)C(R′)NCH 3, where R, R′ = H, H; H, CH 3; CH 3, CH 3; CH 3, C 2H 5; CH 2CH 2CH 2CH 2; CH 2CH(CH 3)CH 2CH 2; H, C 6H 5; CH 3, C 6H 5, and mixed diimine ligands, L = C 5H 4NC(R 1)N(R 2), where R 1, R 2 = H, CH 3; H, C 2H 5; CH 3, CH 3; CH 3, C 2H 5; CH 3, C 6H 5; CH 3, m- or p-NH 2C 6H 4; C 6H 5; CH 3, m- or p-NH 2C 6H 4; C 6H 5, C 6H 5; C 6H 5, m- or p-NH 2C 6H 4 was studied by means of cyclic voltammetry in acetonitrile, 0.2 M tetra-ethylammonium perchlorate at 25.0 °C. Except for compounds R, R′ = H, C 6H 5; CH 3, C 6H 5, and for the compounds with free amino groups, reversible one-electron oxidation processes were found. For the amino containing compounds the electrochemical oxidation is more complex due to concurrent oxidation of the amino group. For the phenyl derivatives of the aliphatic series, chemical and electrochemical steps follow the primary reversible one-electron reaction. For the compounds which exhibit reversible electrochemical oxidation, the half-wave potentials are identical to the standard electrode potentials. These potentials can be correlated with the sum of the polar Taft parameters for the substituents. Substituents presenting large steric or mesomeric effects do not fit this correlation, since these effects are excluded from the polar Taft parameters. A better correlation can be obtained by including steric effects. The frequencies of the intense absorption band in the visible region, assigned to an inverse charge transfer, are correlated with the half-wave potentials of the reversible oxidation processes. A correlation between the square-foot of the molar absorpivities at the absorbance maximum of the inverse charge transfer band with the sum of the polar Taft parameters of the substituents is also obtained.

Ligand oxidation in iron diimine complexes. 3. Electrochemical oxidation of tris(glyoxal bis(methylimine))iron(II)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTLigand oxidation in iron diimine complexes. 3. Electrochemical oxidation of tris(glyoxal bis(methylimine))iron(II)Helena Li. Chum, T. Rabockai, J. Phillips, and R. A. OsteryoungCite this: Inorg. Chem. 1977, 16, 4, 812–815Publication Date (Print):April 1, 1977Publication History Published online1 May 2002Published inissue 1 April 1977https://doi.org/10.1021/ic50170a017RIGHTS & PERMISSIONSArticle Views48Altmetric-Citations7LEARN 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 (491 KB) Get e-Alerts Get e-Alerts

Cyclic voltammetry of iron diimine complexes in acetonitrile

The electrochemical behavior of iron diimine complexes, (H3C−N=C(R)−C(R′)=N−CH3)3Fe(II) (R, R′=H,H;H, CH3; CH3, CH3), and (C5H4N−C(R1)=N(R2))3Fe(II) (R1, R2=H, CH3; CH3, CH3) on a platinum working electrode in acetonitrile is described, and compared to that of the parent aromatic complex, tris-(2,2′-bipyridine)Fe(II). One-electron reversible oxidations were found for all the compounds studied. The electrochemical reductions show 2–3 reduction waves in the potential range studied. Only for the complexes of mixed diimine ligands or 2,2′-bipyridine, a pre-adsorption wave is also observed. It is possible to stabilize low valence states with all ligands studied. A formal iron(I) state is described for the first time for all aliphatic diimine complexes, thus showing that the acceptor properties of the diimine complexes do not depend on the presence of the aromatic rings, but on the iron-diimine chromophore.

Cyclic voltammetry of iron dimine complexes in acetonitrile

The electrochemical behavior of iron diimine complexes, (H 3C−N=C(R)−C(R′)=N−CH 3) 3Fe(II) (R, R′=H,H;H, CH 3; CH 3, CH 3), and (C 5H 4N−C(R 1)=N(R 2)) 3Fe(II) (R 1, R 2=H, CH 3; CH 3, CH 3) on a platinum working electrode in acetonitrile is described, and compared to that of the parent aromatic complex, tris-(2,2′-bipyridine)Fe(II). One-electron reversible oxidations were found for all the compounds studied. The electrochemical reductions show 2–3 reduction waves in the potential range studied. Only for the complexes of mixed diimine ligands or 2,2′-bipyridine, a pre-adsorption wave is also observed. It is possible to stabilize low valence states with all ligands studied. A formal iron(I) state is described for the first time for all aliphatic diimine complexes, thus showing that the acceptor properties of the diimine complexes do not depend on the presence of the aromatic rings, but on the iron-diimine chromophore.

ChemInform Abstract: SUBSTITUENT EFFECTS ON IRON DIIMINE COMPLEXES. I. CORRELATIONS WITH THERMODYNAMIC AND SPECTRAL PROPERTIES IN AQUEOUS SULFURIC ACID

Chemischer InformationsdienstVolume 7, Issue 40 Article ChemInform Abstract: SUBSTITUENT EFFECTS ON IRON DIIMINE COMPLEXES. I. CORRELATIONS WITH THERMODYNAMIC AND SPECTRAL PROPERTIES IN AQUEOUS SULFURIC ACID H. LI CHUM, H. LI CHUMSearch for more papers by this authorT. RABOCKAI, T. RABOCKAISearch for more papers by this author H. LI CHUM, H. LI CHUMSearch for more papers by this authorT. RABOCKAI, T. RABOCKAISearch for more papers by this author First published: October 5, 1976 https://doi.org/10.1002/chin.197640073Read the full textAboutPDF 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. Volume7, Issue40October 5, 1976 RelatedInformation

Substituent effects on iron diimine complexes. I. Correlations with thermodynamic and spectral Properties in aqueous sulfuric acid

Substituent effects on iron complexes FeL 3 2+, of aliphatic diimine ligands, H 3CNC(R)C(R′)Nz.sbnd;CH 3 (R,R′= H,H; H,CH 3; CH 3, CH 3; CH 3, C 2H 5;CH 2CH 2 CH 2CH 2; CH 2CH(CH 3)CH 2CH 2) or mixed diimine ligands, C 5H 4NC(R 1)N(R 2), (R 1,R 2=H,CH 3; H,C 2 H 5; H,n-C 3H 7; CH 3,CH 3; CH 3C 2H 5; CH 3,N-C 3H 7; C 6H 5CH 3) are reported. Formal electrode potentials were obtained in 4.0M H 2SO 4 and shown to correlate with Σσ* Taft polar parameters, except for substituents presenting large steric effects. Except for the n-propyl derivatives, it was possible to correlate all other compounds by considering that steric effects, E s, were also additive. The failure to include the n-propyl data shows that steric effects within the iron diimine grouping are larger than could be accounted for by the simple steric parameters used. Good linear free-energy relationships are also obtained for logε (ε, molar absorptivity) at the maximum wavelength of the inverse charge transfer bands of the ferrous complexes and Σσ*, or logε of the charge transfer bands for the ferric complexes and Σσ*, in the aliphatic series. In the mixed series such correlations were not obtained as a result of a more important role of steric effects. Based on these correlations, estimates of Σσ* and E s for the cyclohexanedione derivatives were also obtained.