FeIII Cl Research Articles

An Iron Macrocyclic Complex Containing Four "Hybrid" Pyridinium Amidate/Amidate N-Donors as a Catalyst for Oxidations With Hydrogen Peroxide.

The macrocyclic pro-ligand [H4L][OTf]2, which contains four carboxamide functions and two conjugated pyridinium groups, is easily deprotonated by the weak base sodium acetate to give the corresponding neutral pro-ligand [H2L]. Metalation of [H2L] with iron(II) chloride proceeds rapidly to form the macrocyclic complex, [FeIIICl(L)]. This is an effective catalyst for the oxidation of the organic dye orange II by hydrogen peroxide in aqueous solution and the kinetic parameters for this reaction have been determined. In striking contrast to an analogous iron-TAML complex that contains two phenyl groups in place of the two pyridinium groups, [FeIIICl(L)] is a very active oxidation catalyst at pH 7 and is also highly stable towards acid promoted demetallation at pH 5 or above. The results show that the two pyridinium groups bring greatly enhanced catalytic properties to [FeIIICl(L)].

Highly Robust Iron Catalyst System for Intramolecular C(sp3 )-H Amidation Leading to γ-Lactams.

Disclosed here is the use of an iron catalyst system for an intramolecular C-H amidation toward γ-lactam synthesis from dioxazolone precursors. (Phthalocyanine)FeIII Cl was found to catalyze this cyclization with extremely high turnover numbers of up to 47 000 under mild and aerobic conditions. On the basis of experimental and computational mechanistic studies, the reaction is suggested to proceed by a stepwise radical pathway involving fast hydrogen atom abstraction followed by radical rebound. A plausible origin for the high turnover numbers along with air-compatibility is also rationalized.

Atom transfer radical polymerization (ATRP) and organometallic mediated radical polymerization (OMRP) of styrene mediated by diaminobis(phenolato)iron(II) complexes: a DFT study.

This study has addressed the radical polymerization of styrene mediated by the diaminobis(phenolate) complexes [Fe(O-2,4-Y2C6H2-5-CH2)2NCH2CH2NMe2], abbreviated as [Fe(II)]. The system is known to be well controlled when Y = Cl but not when Y = alkyl. The control was proposed to occur by a dual ATRP+OMRP mechanism. We have used DFT calculations to address the Y = Cl and Y = CH3 systems. The growing radical chain, ATRP dormant chain, and OMRP dormant chain were simplified to PhCH(CH3)(•), PhCH(CH3)-Cl, and [PhCH(CH3)-Fe(III)]. The idealized ATRP activation/deactivation equilibrium involves [Fe(III)-Cl] (I(Y)) and PhCH(CH3)(•) on the active side and [Fe(II)] (II(Y)) and PhCH(CH3)-Cl on the dormant side, whereas the OMRP activation/deactivation relates [Fe(II)] and PhCH(CH3)(•) with [PhCH(CH3)-Fe(III)] (III(Y)). A benchmarking of various functionals against the known spin properties of alkylporphyriniron(III) shows B3PW91* to be a suitable functional. For the purpose of bond dissociation energy calculations, a dispersion correction was made (B3PW91*-D3). For both Y systems, the ground state is a spin sextet for I, a spin quintet for II, and a spin quartet for III. The calculations show a greater energy cost for the ATRP activation process involving Cl atom addition to II(Cl) to yield I(Cl) (7.2 kcal/mol) relative to the process transforming II(Me) to I(Me) (2.1 kcal/mol). On the other hand, the alkyl addition transforming II to III provides slightly greater stabilization for II(Cl) (27.1 kcal/mol) than for II(Me) (26.1 kcal/mol). As a result, both ATRP and OMRP trapping processes provide greater stabilization for the Y = Cl system, in agreement with the observed better control. The charge analysis attributes these minor but determining energy differences to the inductive electron withdrawing effect of the phenolato Cl substituents. The ATRP and OMRP activation/deactivation pathways have been analyzed in relation to the spin state change; they show in each case the absence of an activation barrier, and both processes corresponding to spin allowed single-state pathways occurring on the quartet (OMRP) and quintet (ATRP) potential energy surfaces. Molecular volume calculations suggest that the balance between ATRP and OMRP may shift in favor of the latter at higher pressures.

Synthesis and structure of iron (III) and iron (II) complexes in S 4P 2 environment created by diethyldithiocarbamate and 1,2-bis(diphenylphosphino)ethane chelation: Investigation of the electronic structure of the complexes by Mössbauer and magnetic studies

Iron (II) and iron (III) complexes, [Fe II(DEDTC) 2(dppe)] · CH 2Cl 2 ( 1), [Fe II(ETXANT) 2(dppe)] ( 2) (DEDTC = diethyldithiocarbamate, ETXANT = ethyl xanthate, dppe = 1,2-bis (diphenylphosphino) ethane), and [Fe III(DEDTC) 2(dppe)] [Fe IIICl 4] ( 3) have been synthesized and characterized. Since 3 contains two magnetic centers, an anion metathesis reaction has been conducted to replace the tetrahedral FeCl 4 − by a non-magnetic BPh 4 − ion producing [Fe III(DEDTC) 2(dppe)]BPh 4 ( 4) for the sake of unequivocal understanding of the magnetic behavior of the cation of 3. With the similar end in view, the well-known FeCl 4 − ion, the counter anion of 3, is trapped as PPh 4[Fe IIICl 4] ( 5) and its magnetic property from 298 to 2 K has been studied. Besides the spectroscopic (IR, UV–Vis, NMR, EPR, Mass and XPS) characterization of the appropriate compounds, especially 2, others viz. 1, 3 and 4 have been structurally characterized by X-ray crystallography. While Fe II complexes, 1 and 2, are diamagnetic, the Fe III systems, namely the cations of 3, and 4 behave as low-spin (S = 1/2) paramagnetic species from 298 to 50 K. Below 50 K 3 shows gradual increase of χ M T up to 2 K suggesting ferromagnetic behavior while 4 exhibits gradual decrease of magnetic moment from 60 to 2 K, indicating the occurrence of weak antiferromagnetic interaction. These conclusions are supported by the Mössbauer studies of 3 and 4. The Mössbauer pattern of 1 exhibits a doublet site for diamagnetic (2–400 K) Fe II. The compounds 1, 2 and 4 encompass interesting cyclic voltammetric responses involving Fe II, Fe III and Fe IV.

Synthesis and characterization of monomer and dimer complexes of porphyrin iron(III) with bridging phenylcyanamide ligands

Several new mono and dinuclear complexes of [(P)Fe III(L)], in which P is the dianion of tetraphenylporphyrin(TPP) and tetramesitylporphyrin(TMP) and L is the monoanion of 4-azo(phenylcyanamido)benzene (apc) ( 1) and ( 2) or dianion 1,4-di cyanamidobenzene (dicyd) ( 3), ( 4), ( 7), ( 8) and 4,4′-azo-diphenylcyanamide (adpc) ( 5), ( 6), ( 9), ( 10) have been prepared by the reaction of [(P)Fe IIICl] with appropriate thallium salts of phenylcyanamide derivatives. Each of the complexes has been characterized by FT-IR, UV–Vis, 1H NMR, MALDI-TOF and EPR spectroscopic data. In non-coordinating solvents (such as toluene or chloroform) these complexes exhibit 1H NMR spectra that are characteristic of high-spin (S = 5/2) species. The cyanamide group (NCN) of the bridging ligand is coordinated to Fe(III) ions through the nitrile-nitrogen. The iron(III) phenylcyanamide complexes are not reactive toward dioxygen, they convert into [TPPFe IIICl] when treated with HCl. EPR and NMR have shown that in dinuclear complexes weak magnetic interactions take place between two iron(III) paramagnetic centers.

Catalytic oxidation of limonene, α-pinene and β-pinene by the complex [Fe III(BPMP)Cl(μ-O)Fe IIICl 3] biomimetic to MMO enzyme

The catalytic oxidation of limonene, α-pinene and β-pinene was studied using the complex [Fe III(BPMP)Cl(μ-O)Fe IIICl 3] biomimetic to MMO enzyme as catalyst, and hydrogen peroxide as oxidant. The reaction products were identified by gas chromatography coupled with a mass spectrometer detector. Full factorial 2 3 experimental designs were used to assess the influence of reaction time, oxidant and catalyst levels on the reaction conversion. The results indicated that the complex exhibit good catalytic activity towards limonene, β-pinene and α-pinene, where significant conversions were observed. The main products of limonene, β-pinene and α-pinene oxidation were carvone, pinocarvone and verbenone, respectively.

A Green Process for Oxidation of p-Nitrotoluene Catalyzed by Metalloporphyrins under Mild Conditions

A novel synthetic technology of p-nitrobenzoic acid has been investigated with dioxygen by using metalloporphyrins RTPPMIIICl (M = Fe, Co, Mn) as biomimetic catalysts. Oxidation of p-nitrotoluene to p-nitrobenzoic acid under 2.0 MPa of O2 in the presence of a microamount of metalloporphyrins (RTPPMIIICl) at 55 °C was achieved with the highest (up to 90.4%) yield. Further research results show that the catalytic activities were relative to the nature of the substituted groups and the central metal ions of metalloporphyrins. For the metalloporphyrins with the same center metal ions, the greater the electron-withdrawing degree of groups in the porphyrin ring, the higher the catalytic activities of the metalloporphyrins. The catalytic activities for metalloporphyrins with different center metal ions followed the order RTPPMn IIICl >RTPP Fe IIICl > RTPP Co IIICl.

Synthesis and characterization of tetraphenylporphyrin iron(III) complexes with substituted phenylcyanamide ligands

Several five coordinate complexes of [(TPP)Fe III(L)] in which TPP is the dianion of tetraphenylporphyrin and L is the monoanion of phenylcyanamide (pcyd) ( 1), 2,5-dichlorophenylcyanamide (2,5-Cl 2pcyd) ( 2), 2,6-dichlorophenylcyanamide (2,6-Cl 2pcyd) ( 3), and 2,3,4,6-tetrachlorophenylcyanamide (2,3,4,6-Cl 4pcyd) ( 4) have been prepared by the reaction of [(TPP)Fe IIICl] with appropriate thallium salt of phenylcyanamide. Each of the complexes has been characterized by IR, UV–Vis and 1H NMR spectroscopic data. Dark red-brown needles of [(TPP)Fe III(2,6-Cl 2pcyd)] (C 51H 31Cl 2FeN 6 · CHCl 3) crystallize in the triclinic system. The crystal structure of Fe(III) compound shows a slight distortion from square pyramidal coordination with the 2,6-dichlorophenylcyanamide anion in the axial position through nitrile nitrogen atom. Iron atom is 0.47(1) Å out of plane of the porphyrin toward phenylcyanamide ligand. In non-coordinating solvents, such as benzene or chloroform, these complexes exhibit 1H NMR spectra that are characteristic of high-spin ( S = 5/2) species. The X-ray crystal structure parameters are also consistent with high-spin iron(III) complexes. The iron(III) phenylcyanamide complexes are not reactive toward molecular oxygen; however, these complexes react with HCl and produce TPPFe IIICl.

Preparation and characterization of three types of dinuclear iron(III) complexes with H 2salbn, N, N′-disalicylidene-1,4-diaminobutane

By the reaction of the tetradentate Schiff base ligand H 2salbn, N, N ′-disalicylidene-1,4-diaminobutane with Fe IIICl 3·6H 2O in the presence of Et 3N in MeOH a dinuclear iron(III) complex, [Fe III(salbn)(μ-OMe)] 2 ( 1), has been obtained, whereas in EtOH, dinuclear complexes, [Fe III(μ-salbn)] 2(μ-O) ( 2) and [Fe III(salbn)] 2(μ-salbn) ( 3), are obtained. The structure of the complex 1 consists of two Fe(III) centers with one tetradentate salbn ligand (N 2O 2) which are bridged by two methoxo groups to yield a planar Fe 2O 2 core. On the other hand, in the complex 2, each of the two Fe(III) ions has a five-coordinate structure in which both salbn ligands act as a bridging didentate ligand and one oxygen atom bridges two Fe(III) ions to form a μ-oxo structure. The structure of the complex 3, which was obtained by accompanying with complex 2, consists of two six-coordinate Fe(III) centers in which each Fe(III) ion is coordinated by a tetradentate salbn ligand (N 2O 2) and one bridging salbn ligand (NO).

CHITOSAN--IRON(III)--CROSSLINKING (CH–FeIII–CL) FOR PRE-CONCENTRATION OF PHOSPHATE IN SIMULATED SEAWATER

In this work, the pre-concentration of phosphate on chitosan–iron(III)–crosslinked (CH–FeIII–CL) was investigated in simulated seawater. The results from the sorption experiments demonstrate the possibility of using CH–FeIII–CL to remove phosphate from seawater. Improved analytical performance for phosphate pre-concentration using the CH–FeIII–CL method was obtained compared to the conventional method. Based on the results, the methods will be applied to analyze river water, seawater, groundwater, and industrial water.

Unique tetranuclear copper(II) cluster and monomeric iron(II), (III) complexes with a tris(imidazolyl) chelating ligand

Copper(II) and iron(II, III) complexes of the tripodal ligand, tris(1-methyl-1 H-imidazol-2-yl)methanol (Htmim), have been synthesized and characterized by elemental analysis, 1H NMR and IR spectroscopies, magnetic moment measurement and X-ray crystallography. The structure of the copper complex, [Cu 4(tmim) 4(CF 3SO 3) 2](CF 3SO 3) 2·2MeOH ( 1), can be regarded as a polyimidazole-linked tetranuclear cluster where each copper atom adopts a five-coordinate square-pyramidal geometry ligated by the tmim anion. The two iron complexes, [Fe II(Htmim) 2][Fe IICl 4]·4MeOH ( 2) and [Fe III(Htmim) 2][Fe IIICl 4] 2Cl ( 3), contain the isostructural [Fe(Htmim) 2] cation and tetrahedral [FeCl 4] − anion. While Htmim shows a normal tripodal tridentate mode in the iron complexes capping one face of an essentially octahedral coordination sphere, its deprotonated species exhibit an unusual non-tripodal tetradentate coordination with copper(II) ions. The observed magnetic moment at room temperature for 1 is 1.13 BM per Cu atom, consistent with antiferromagnetic coupling between the copper(II) atoms of the tetramer. Both 2 and 3 show magnetic properties consistent with low-spin electronic configurations of the cation and high-spin nature of the metal ion in the anion.

Mechanisms for (porphyrinato)iron(III)-catalyzed oxygenation of styrenes by O 2 in presence of BH −4

Mechanisms have been proposed for the (porphyrinato)iron(III)-catalyzed oxidation of styrene and α-methylstyrene by O 2 in benzene-ethanol containing NaBH 4. The product analysis and the deuterium incorporation using NaBD 4 suggest that the (σ-alkyl)Fe IIIPor complex, [C 6H 5CH(CH 3)]Fe IIIPor, is formed as an intermediate in the reaction of styrene. Insertion of O 2 to the (σ-alkyl)Fe IIIPor complex having a radical character yields a (peroxy)iron(III) complex, [C 6H 5CH(CH 3)OO]Fe IIIPor. The homolytic fission of the OO bond followed by the hydrogen abstraction within the radical pair affords acetophenone and (HO)Fe IIIPor. Acetophenone is readily reduced with NaBH 4 to give l-phenylethanol. Meanwhile, the reaction of α-methylstyrene with BH − 4 in the presence of PorFe IIICl may also yield the (σ-alkyl)Fe IIIPor complex, which takes up O 2 to form a (peroxy)iron(III) complex, (C 6H 5C(CH 3) 2OO)Fe IIIPor. The (peroxy)iron(III) complex is directly reduced by BH − 4 to give 2-phenyl-2-propanol and (HO)Fe IIIPor. In the reaction of styrene, such direct reduction of the (peroxy)iron(III) complex as a minor pathway competes with the homolytic fission of its OO bond.

Redox reactions between oxomolybdenum(IV) and tetratolylporphinatoiron(III) complexes

The coupling of an Mo VIO 2→Mo IVO oxygen atom transfer reaction to a one-electron reoxidation of the resulting Mo(IV) center by an Fe(III) porphyrin center has been investigated in an attempt to model the first two redox steps in the catalytic cycle of the enzyme sulfite oxidase. Reaction of LMo VIO 2Cl (L=hydrotris(3,5-dimethyl-1-pyrazolyl)borate) with excess tri-phenylphosphine in DMF rapidly and cleanly generates LMo IVOCl(DMF). This Mo(IV) species reacts more slowly with Fe IIICl(TTP) (TTP=tetratolylporphyrin) to give LMo VOCl 2 and Fe II(TTP) as the final products. The kinetics of this one-electron redox reaction have been followed by electronic spectroscopy and by 1H NMR. The reaction is zero-order in Fe(III), first-order in Mo(IV), and independent of added chloride ion. The first-order rate constant determined by these methods ranged from 1.7−4.6×10 −5 s −1. An inner-sphere (halogen transfer) mechanism is shown to be most consistent with the data.

Synthesis and characterization of some novel pentagonal bipyramidal 2,6-diacetylpyridine bis(benzoylhydrazone) (DAPBH 2) complexes of Rhenium(III) and molybdenum crystal and molecular structure of [ReCl(DAPB)(PPh 3)]. An investigation of the Mössbauer spectroscopy of [Fe IICl 2(DAPBH 2)]·H 2O and [Fe IIICl(DAP-Me-B)(H 2O)

Reaction of [ReCl 3(MeCN)(PPh 3) 2] with the planar pentadentate diacetylpyridinebis(benzoylhydrazone) ligands DAPBH 2 and DAP-Me-BH 2 and triethylamine in isopropanol under reflux gave the dark brown seven-coordinate complexes [ReCl(L)PPh 3], containing the doubly deprotonated pentadentate ligand [L = DAPB(2−)( 1); L = DAP-Me-B(2−) ( 2)]. Complex 1 has been characterized by crystallography. The central rhenium atom in 1 is seven-coordinate, with pentagonal bipyramidal geometry with the axial positions being occupied by the chloride ion and the triphenylphosphine ligand. The DAPB coordinates in a pentadentate manner in the equatorial plane of the complex and the five donor atoms of the doubly deprotonated DAPB(2−) ligand form an approximately planar pentagon. The rhenium atom is slightly displaced out of the ligand plane towards the phosphorus atom. Reaction of 2 with Ag[BF 4] in CH 2Cl 2 at room temperature gave a black complex of stoichiometry [Re(DAP-Me-B)(PPh 3)][BF 4] ( 3). Reaction of [MoCl 4(MeCN) 2] with DAP-Me-BH 2 and Et 3N in dry CH 2Cl 2 under reflux gave deep green [MoCl 2(DAP-MeB 2)] ( 4), formulated as a seven-coordinate molybdenum(II) complex containing the doubly deprotonated pentadenate DAP-MeBH 2 ligand in the equatorial plane of the complex. The Mössbauer spectra of the complexes [FeCl 2(DAPBH 2)]·H 2O ( 5) and [FeCl(DAPMe-B)(H 2O)] ( 6) were investigated as a function of temperature. The spectrum of 5 was consistent with high-spin seven-coordinate iron(II) and 6 was shown to contain two distinct iron(III) sites; possible structures are discussed.

Investigation of the intermediates in the oxidation of a bulky arylphosphine ligand with ferric chloride

The syntheses, spectroscopic properties and structures of iron(II) and iron(III) complexes prepared by reactions of ferric chloride with the tertiary phosphine ligand tris(2,4,6-trimethoxyphenyl)phosphine (TMPP) are described. The novel diferrous chloride salt [H-TMPP] 2[Fe 2Cl 6] ( 1) was prepared by the reaction of anhydrous ferric chloride with 1 equivalent of TMPP in benzene or diethyl ether. This redox reaction also produces [TMPP-Cl][FeCl 4] ( 2) as the oxidized by-product. The structure of 1, determined by single-crystal X-ray diffraction, revealed that the [Fe 2Cl 6] 2− anion consists of two edge-sharing tetrahedra with two terminal and two bridging chlorides per metal atom. Dissolution of complex 1 in ethanol produces [H-TMPP] 2[Fe IICl 4] ( 3), which was identified on the basis of a preliminary X-ray investigation. Compound 3, independently prepared by the reaction of [Fe(NCCH 3) 6][AlCl 4] 2 with 2 equivalents of TMPP in methanol, reacts with molecular oxygen to initially form [H-TMPP][Fe IIICl 4] ( 4) and finally the phosphine oxide species FeCl 3(OTMPP) ( 5). The structure of 4 was determined by single-crystal X-ray diffraction. To test the importance of compound 4 as an intermediate in the production of TMPPO, it was prepared directly by reaction of [Fe(NCCH 3) 6][SbCl 6] 2 with 2 equivalents of TMPP in methanol and reacted with oxygen to give 5 in high yield. Compounds 1– 5 were further characterized by IR and electronic spectroscopies, as well as by elemental analyses. The reactions of the salts 1, 3 and 4 suggest that the oxidation of tertiary arylphosphines with FeCl 3 in alcohols does not proceed via the formation of dioxygen complexes, but rather via quaternarization of the phosphine ligand.

Hydrogen peroxide oxidation of Fe 2(ttha) 2−: a path different from autoxidation

Fe II2(ttha)(H 2O) 2 2− is oxidized rapidly by H 2O 2, but greater than a 1:1 stoichiometric consumption of H 2O 2 occurs. While the oxidation product of O 2/Fe 2(ttha)(H 2O) 2 2− is greater than 95% Fe 2O(ttha) 2−, the H 2O 2 oxidation products include c. 80% Fe III 2O(ttha) 2−, c. 20% of a tetranuclear complex Fe III 4(O) 2(ttha) 2 4−, and traces of Fe IIICl 4 − and Fe III(tthaH) 2−. The Fe II 2(ttha)(H 2O) 2 2− oxidation by H 2O 2 exhibits only a 6.8% suppression in the presence of 0.10 M t-butanol instead of a 50% suppression if production of HO · is a major pathway in the H 2O 2 oxidation. The mechanism is proposed to occur via formation of ferryl intermediates which may react with the second iron(II) site within the same molecule by an inner-sphere route forming the μ-oxo bridged Fe III 2O(ttha) 2− or by outer-sphere electron transfer forming an open-chain Fe III 2(ttha)(H 2O) 2 complex. The same ferryl intermediate may react inner-sphere with a second Fe III 2(ttha)(H 2O) 2 2− complex, leading to the tetranuclear product. The pathways which yield Fe 2O(ttha) 2− upon ring closure of open-chain Fe III 2(ttha)(H 2O) 2 involve three parallel pathways utilizing aqua/aqua, aqua/hydroxy and hydroxyl/hydroxy forms of [Fe III 2(ttha)] with first-order rate constants of 12.0, 11.6 and 0.11 s −1, respectively (μ=0.05, T=25.0 °C). The abnormally high reactivity of the aqua-aqua species for μ-oxo formation is consistent with a hydrogen-bonded orientation of Fe III 2(ttha)(OH 2) 2 within its own solvent cage which places the Fe III centers close for μ-oxo formation. A peroxo complex forms via substitution at a terminal site of Fe III 2(OH) 2 2− with a second-order rate constant of 4.32±0.20 M −1 s −1. A slower first-order rearrangement of the initial peroxo adduct is observed ( k=0.14±0.02 s −1) with an [H 2O 2]- independent rate. A rearrangement from an initial η 2-peroxo coordination to an η 1:η 1 (bridged) coordination is proposed. The peroxo species of [Fe III 2(ttha)] which is isolated by ethanol-induced precipitation from solution containing 13.6:1.0 H 2O 2:Fe III 2(ttha)(H 2O) 2 exhibits a new band at 791 cm −1, consistent with η 1:η 1 coordination based on [Co III 2(H 2O) 2(O 2)(histidinate) 4] as a model. Although the η 2-peroxo complex [Fe III(O 2)(edta)] 3− exhibits a purple color due to an LMCT band at 528 nm, neither [Fe 2(O 2)(ttha)] 2−, nor [Fe III(hedta)(O 2)] 2− possess a band above 500 nm, a feature frequently attributed as diagnostic of ferric peroxo species with polyaminopoly- carboxylate ligands. [Fe III(hedta)(O 2)] 2− is observed to be golden-brown at pH 10.30 and to have the anticipated ν(OO) stretch at 810 cm −1 for the η 2-peroxo complex. Yet it has no LMCT band above 440 nm.

Selective dehydrogenation (oxidation) of 3,4-dimethoxybenzyl alcohol by a non-heme iron lignin-peroxidase reaction mimic

In pyridine, bis(2,2′-bipyridine)iron(II) (Fe(bpy) 2+ 2) activates hydrogen peroxide for the efficient and selective catalytic dehydrogenation (oxidation) of veratryl alcohol (model-substrate monomer for lignin; 3,4-(MeO) 2PhCH 2OH). Several other complexes (Fe II(OPPh 3) 2+ 4, Fe II(O 2bpy) 2+ 2, Fe II(MeCN) 2+ 4, Fe II(PA) 2, Fe IIICl 3) are effective catalysts for the dehydrogenation of veratryl alcohol and benzyl alcohol, but their selectivity (relative reactivity with 3,4-(MeO) 2PhCH 2OH vs. PhCH 2OH) is less than the 6.1 ratio that is observed for the optimized Fe II(bpy) 2+ 2/H 2O 2/pyridine(py) system. The reactivities have been determined for several other methoxybenzyl alcohols that are model substrates for lignin (e.g.,4-MeOPhCH 2OH and (MeO) 3PhCH 2OH).

Photocatalytic cleavage of 1,2-diols by a cofacially hindered water-soluble iron(III) porphyrin

The photocatalytic decompositions of 1,2-diols by newly synthesized [meso-tetrakis(3,5-dichloro-1-methyl-4-pyridiniumyl)porphyrinato] iron(III) Fe IIICl 2MPyP were compared with those by [meso-tetrakis(1-methyl-4-pyridiniumyl)porphyrinato]iron(III) Fe IIITMPyP, Cofacially hindered FeTCl 2MPyP was more robust and substrate-specific than FeTMPyP.

Methods for investigating the mechanistic and kinetic role of ligand exchange reactions in coordination electrochemistry: Cyclic voltammetry of chloroiron(III)tetraphenylporphyrin in dimethylformamide

The two successive reductions of chloroiron(III)tetraphenylporphyrin in dimethylformamide provide a model example illustrating the use of cyclic voltammetry for investigating the role of ligand exchange reactions in the electrochemistry of coordination compounds. The Cl −-DMF association constant for Fe II is determined spectrometrically. The Cl −-DMF association constant for Fe III is then derived from the standard potential difference between the [Fe III (DMF) 2] +/[Fe IIDMF] and [Fe IIICl]/[Fe IICl] − redox couples. Starting from the values thus obtained, the kinetics of the Cl −-DMF ligand exchange reaction at the Fe III and Fe II oxidation levels are investigated using cyclic voltammetry. Both the reduction and oxidation of the Fe II complexes into Fe I and Fe III respectively can be used for this purpose, under pseudo-first order conditions in the first case and second order conditions in the second. Development and application of the theory for a CEC square scheme under second order conditions allowed the role of the ligand exchange reaction in the reduction of the Fe III complexes to be unraveled.

Étude cristallographique du tétrachloroferrate(III) d'hexaacétonitrile-fer(II)

Fe 3Cl 8(NCCH 3) 6, has been crystallized from a solution of ferric chloride in acetonitrile. The trigonal unit cell, a = 11.69 ± 0.01 Å and c= 6.130 ± 0.007 Å space group P 3 , contains two tetrahedrons (Fe IIICl 4) − and one octahedron [Fe II(NCCH 3) 6] 2+. Microtwinning occurs in such a way that ( h0 h0 ) planes become mirror images since each orientation is approximately 50%. The structure has been solved from 921 reflections recorded at room temperature. Inverting the whole matrix of normal equations, and taking anisotropic temperature factors, gives an R value of 0.045 if 45 zero reflexions are excluded. An examination of distances and angles shows a close structural analogy between (FeCl 4) 2[Fe(NCCH 3) 6] and (FeCl 4) 2[Fe(NCH) 6].