A structural and Mössbauer study of complexes with Fe(2)(micro-O(H))(2) cores: stepwise oxidation from Fe(II)(micro-OH)(2)Fe(II) through Fe(II)(micro-OH)(2)Fe(III) to Fe(III)(micro-O)(micro-OH)Fe(III)

Dinuclear non-heme iron clusters containing oxo, hydroxo, or carboxylato bridges are found in a number of enzymes involved in O(2) metabolism such as methane monooxygenase, ribonucleotide reductase, and fatty acid desaturases. Efforts to model structural and/or functional features of the protein-bound clusters have prompted the preparation and study of complexes that contain Fe(micro-O(H))(2)Fe cores. Here we report the structures and spectroscopic properties of a family of diiron complexes with the same tetradentate N4 ligand in one ligand topology, namely [(alpha-BPMCN)(2)Fe(II)(2)(micro-OH)(2)](CF(3)SO(3))(2) (1), [(alpha-BPMCN)(2)Fe(II)Fe(III)(micro-OH)(2)](CF(3)SO(3))(3) (2), and [(alpha-BPMCN)(2)Fe(III)(2)(micro-O)(micro-OH)](CF(3)SO(3))(3) (3) (BPMCN = N,N'-dimethyl-N,N'-bis(2-pyridylmethyl)-trans-1,2-diaminocyclohexane). Stepwise one-electron oxidations of 1 to 2 and then to 3 demonstrate the versatility of the Fe(micro-O(H))(2)Fe diamond core to support a number of oxidation states with little structural rearrangement. Insight into the electronic structure of 1, 2', and 3 has been obtained from a detailed M?ssbauer investigation (2' differs from 2 in having a different complement of counterions). Mixed-valence complex 2' is ferromagnetically coupled, with J = -15 +/- 5 cm(-)(1) (H = JS(1).S(2)). For the S = (9)/(2) ground multiplet we have determined the zero-field splitting parameter, D(9/2) = -1.5 +/- 0.1 cm(-)(1), and the hyperfine parameters of the ferric and ferrous sites. For T < 12 K, the S = (9)/(2) multiplet has uncommon relaxation behavior. Thus, M(S) = -(9)/(2) <--> M(S) = +(9)/(2) ground state transition is slow while deltaM(S) = +/-1 transitions between equally signed M(S) levels are fast on the time scale of M?ssbauer spectroscopy. Below 100 K, complex 2' is trapped in the Fe(1)(III)Fe(2)(II) ground state; above this temperature, it exhibits thermally assisted electron hopping into the state Fe(1)(II)Fe(2)(III). The temperature dependence of the isomer shifts was corrected for second-order Doppler shift, obtained from the study of diferrous 1. The resultant true shifts were analyzed in a two-state hopping model. The diferric complex 3 is antiferromagnetically coupled with J = 90 +/- 15 cm(-)(1), estimated from a variable-temperature M?ssbauer analysis.     

Synthesis and Magnetic Properties of Fe(II) and Nd(III) Complexes of Poly(N-2-thiazolylacrylamide)

In recent years,the organic ferromagnets have drawn growing attention due to their characteristics of structural diversities,low density,and readily processing1-3.Design and synthesis of magnetic polymers are one of great challenges in today′s magnetic material research,and some significant achievements have been made in this field4,5.In this article,we describe the synthesis of acrylamide-type polymer with pendent thiazolyl groups(Scheme1).The as-prepared polymer exhibited better solubility …     

Phosphine-centred resolution of (η4-diene)Fe(CO)3 complexes: (η4-tropone)Fe(CO)2L and (η4-isoprene)Fe(CO)2L [L = (+)-(neomenthyl)PPh2]

(η⁴-Tropone)Fe(CO)₃ and (η⁴-isoprene)Fe(CO)₃ form separable diastereoisomers on substitution of CO by (+)-(neomenthyl)PPh₂. In the tropone complex, diastereoisomer interconversion occurs by a 1,3-metal shift. The absolute configuration of the isoprene complex has been determined crystallographically.     

Acetylene as a ligand on clusters: An accurate determination of the crystal and molecular structure of (Cp)2Ni2Fe(CO)3(μ3−C2H2) and of (CP)2Ni2Fe2(CO)6(μ4−C2H2)

Abstarct The Cp)₂Ni₂Fe(CO)₃(µ₃-C₂H₂) and Cp)₂Ni₂Fe(CO)₃(µ₃-C₂H₂) (B) complexes have been synthesized and spectroscopically characterized. An accurate X-ray study and a comparison with related structures shows that the substituents of the alkyne ligands exert considerable effects on the bonding parameters.Crystal data for complex A, monoclinic space group P2₁/n,a = 8.418(1),b = 15.779(2),c = 14,493(1) Å, = 91.64(1)°,Z = 4, 2753 observed reflections,R = 0.022; crystal data for complex B, monoclinic space group C2/c,a = 16.2189(7),b = 7.445(3),c = 25.745(5) Å, = 103.74(3),Z=8, 1853 observed reflections,R = 0.051.     

Electroconductance of single-crystal Li2 + x Fe 2 − 2x 2+ Fe x 3+ (MoO4)3 (x = 0.22)

Electrophysical properties of single-crystal Li_{2 + x} Fe _{2 ? 2x} ²⁺ Fe _x ³⁺ (MoO₄)₃ (x = 0.22) are studied at 25–400°C. It is found that the conduction is of electronic nature and the conductivity equals 5 × 10^-2 S/cm at 300°C. The activation energy for the electron transport is 0.23 eV. The conductance in molybdate Li_2.22Fe _1.56 ²⁺ Fe _0.22 ³⁺ (MoO₄)₃ is markedly anisotropic.     

Synthesis and X-ray crystal structure analysis of Fe2(CO)6(μ3-S)2Pd(bipy)

The reaction of Fe₂(CO)₆(μ-S₂),1 withbis(dibenzylideneacetone)-palladium, Pd(dba)₂, in the presence of 2,2′-bipyridine yielded the new compound Fe₂(CO)₆(μ ₃-S)₂Pd(bipy),2 in good yield (66%). Compound2 was characterized by IR,¹H NMR and single-crystal X-ray diffraction analyses. Compound2 contains a Pd(bipy) group that has been inserted into the S-S bond of1. Crystal data for2: space group P2₁/n,a=10.019(2) Å,b=25.414(5) Å,c=7.714(2) Å,β=90.26(2)°,Z=4, 1436 reflections,R=0.023.     

Coupling insertion reactions of diphenylbuta-1, 4-diyne into iron-carbene bonds of [Fe2(CO)7{μ-C(Ph)C(NEt2}]. Syntheses and reactivities of the ferracyclopentadiene [Fe2(CO)6{C(Ph)C(NEt2)C(Ph)C(C2Ph)}] with [Fe2(CO)9]

The diiron ynamine complex [Fe₂(CO)₇{-C(Ph)C(NEt₂)}] (1) reacts with the diphenylbuta-1, 4-diyne, PhCC-CCPh, in refluxing hexane to yield three isomer complexes [Fe₂(CO)₆{C(Ph)C(NEt₂)C(Ph)C(C₂Ph}] (2a), [Fe₂(CO)₆{C(Ph)C(NEt₂)C(C₂Ph)C(Ph)}] (2b), and [Fe₂(CO)₆{NEt₂)C(Ph)C(C₂)C(Ph)}] (2c) All three compounds were identified by their¹H NMR spectra. Compounds2a and2c were characterized by single crystal X-ray diffraction analyses. Crystal data: for2a: space group = P2₁/n,a = 17.873(1) Å, = 18.388(6) Å,c = 9.429(3) Å = 91.99(3)°,Z = 4.3751 reflections,R = 0.044; for2c: space group = P2₁/n,a = 40.58(2) å,b = 12.101(9) Å,c = 12.551(5) Å, = 94.29(7)°,Z = 8.4723 reflection,R = 0.076. Complexes2a and2b result from a [2 + 2] cycloaddition between one of the CC triple bonds of the diyne ligand and the FeC carbene bond, whereas2c results from insertion of one of the CC group into the bridging carbene. Addition of [Fe₂(CO)₉] on2a gave two major products, the tripledecker [Fe₃(CO)₈{C(Ph)C(NEt₂)C(C₂Ph)}], (3 and a tetrairon cluster [Fe₄(CO)₁₁{C(Ph)C(NEt₂)C(Ph)C(C₂Ph)}] (4). Both compounds were characterized by single crystal diffraction analyses. Crystal data: for3: space group = P2₁/n,a = 12.039(3) Å,b = 18.046(3) å,c = 15.270(2) Å, = 90.11(2)°,Z = 4, 1430 reflections,R = 0.067; for4 space group = C2/c,a = 18.633(3) Å,b = 21.467(1)_Å,c = 20.742(2) Å, = 115.03(8)°,Z = 8.992 reflections, R = 0.076. Complex4 is based on a spiked triangular cluster with the alkynyl triple bond attached in ₃-parallel mode on the triangular grouping.     

Insertion reactions of t-Bu(η5-C5H5)Fe(CO)2

The complex t-Bu(η⁵-C₅H₅)FE(CO)₂ has been treated with triphenylphosphine in refluxing THF to produce t-BuCO(η⁵-C₅H₅)Fe(CO)(PPh₃). The large steric bulk of the t-butyl group suggests that this reaction should be faster than the reaction involving the methyl group, and a kinetic investigation illustrates this to be the case. The same steric bulk predicts that the reaction with SO₂ should be slow, and indeed we have been unable to effect the related SO₂ insertion reaction. Attempts to prepare the corresponding t-Bu(η⁵-C₅H₅)W(CO)₃ led to formation of the related isobutyl complex.     

Reaction of 2-(diphenylphosphino)-pyridine and -thiazole organoiron(0) polydentate ligands with iron(III) salts: X-ray structures of [η2-Ph2P(O)py]2Fe(μ-Cl)2FeCl2 and Fe(NCS)2[η2-Ph2P(O)taz]2 (taz=thiazole)

The reaction of trans-Fe(CO)₂(CS₂)(Ph₂Ppy-P)₂ (Ph₂Ppy=2-(diphenylphosphino)pyridine) with FeCl₃ resulted in the formation of the binuclear complex [η²-Ph₂P(O)py]₂Fe(μ-Cl)₂FeCl₂ (1), while the reaction of trans-Fe(CO)₃(Ph₂Ptaz-P)₂ (Ph₂Ptaz=2-(diphenylphosphino)thiazole) with Fe(NCS)₃ gave Fe(NCS)₂[η²-Ph₂P(O)taz]₂ (2). The crystal structures of (1) and (2)·C₆H₆ have been determined using X-ray crystallography.     

Spectroscopic and structural properties of homonuclear Fe(II) polymeric compounds.—II. Thermal decomposition products of [Fe(pyrazine)2X2]n

The thermal decomposition of [Fe(pyz)₂X₂]_n (where pyz = pyrazine and X = Cl, Br or I) was investigated. For the chloride and bromide complexes the decomposition proceeds in two stages in which two pyrazine molecules dissociate successively, whereas in the iodide complex both pyrazine molecules dissociate in a single stage. Spectroscopic measurements (UV, Vis, Raman and Mössbauer spectra) indicate that intramolecular rearrangement resulting from dissociation of one pyrazine molecule leads to a change in coordination from FeN₄X₂ characteristic of initial compounds, [Fe(pyz)₂X₂]_n, to FeX₄N₂ characteristic of [Fe(pyz)X₂]_n which is accomplished through both pyrazine and halide bridges. Thus, polymers are being formed in which the (FeX₂)_n chains are being bridged by the pyrazine molecules. The magnetic moments of monopyrazine intermediate compounds are independent of temperature and low-temperature magnetic measurements do not indicate any magnetic ordering above 4.2 K.     

The synthesis of the [Fe(Phen)3](iso-Bu2PS2)2 Complex. The crystal structures of [Fe(Phen)3](iso-Bu2PS2)2 · 5H2O and disulfan {iso-Bu2P(S)S}2

The complex [Fe(Phen)₃][iso-Bu₂PS₂)₂ (I) was synthesized and the single crystals of [Fe(Phen)₃](iso-Bu₂PS₂)₂ · 5H₂O (II) were grown. The disulfan {iso-Bu₂P(S)S}₂ (III) was isolated. Compound II consists of the complex cations [Fe(Phen)₃]²⁺, the outer-sphere anions iso-Bu₂PS ₂ ^? , and the molecules of water of crystallization. The coordination polyhedron of the Fe atom is a distorted N₆ octahedron. Complex I is diamagnetic, and thus, the full spin of the Fe²⁺ ion S = 0. The structure of III is built of the molecules containing the S-S bridge 2.061(1) Å in length.     

Thermal stability of ZrO2–SiO2 aerogel modified by Fe(III) ion

ZrO₂–SiO₂ aerogel modified by Fe(III) ion was prepared and the stability of the samples under high temperature was investigated. The structure and properties of modified aerogels were characterized by N₂ adsorption–desorption, FT-IR, XRD and TEM. The samples still contain a specific surface area about 228 m²/g after 1,000 °C 0.5 h calcinations. The inhibition of ZrO₂ particle growth is attributed to the Fe(III) ion modified aerogel surface, which strongly retards the ZrO₂ tetragonal phase transformation as well.     

A new route to iron(0) thiocarbonyl complex involving desulphurization of the Fe(η2-CS2R)+ cation with P-n-Bu3. Crystal structure of Fe(CS)(CO)2(PPh3)2

Reaction of [Fe(η²-CS₂R)(CO)₂(PPh₃)₂][X] (R = CH₃, CH₂Ph; X⁻ = PF₆⁻, I⁻) with P-n-Bu₃ or PEt₃ gives Fe(CS)(CO)₂(PPh₃)₂ (3a); (ν(CS) 1235 cm⁻¹; δ(¹³C) 324.28 ppm). The structure of 3a has been determined by X-ray diffraction. Crystal data are: a 18.821(5), b 12.113(3), c 18.149(5) Å, β 117.76(6)°, monoclinic, space group P2₁, Z = 4. The structure is a trigonal-bypyramid with equatorial CS group, trans PPh₃ ligands, a FeC(S) bond distance of 1.768(8) and a CS bond distance of 1.563(8) Å.     

Incoporation of Fe(Ⅲ) in framework of zeolite L

Zeolite L with Fe in lattice position is prepared from the gel with Fe/(Fe+Al) ratio up to 0.4 using ferric nitrate as Fe source. The incorporation of Fe(Ⅲ) in framework is characterized by XRD, IR, TG/DTA, BET and Mossbauer spectroscopy. Zeolite L is destabilized by Fe(Ⅲ) in framework and the reduction of Fe(Ⅲ) in framework of (Al,Fe )KL was first reported.     

Kinetics of thermal dehydration and decomposition of Fe(III) chloride hydrate (FeCl3·xH 2O)

Fe(III) chloride hydrate (FeCl₃·xH₂O) undergoes simultaneous dehydration and dehydrochlorination from its molten phase in the temperature range 100–200C. The kinetics of these two parallel thermal processes has been studied by both isothermal and non-isothermal methods. Whereas for the dehydration reaction at temperature below 125C a second order rate model (F₂) fits well, a three-dimensional diffusion (D₃) model is found to fit better at temperature above 135C. For the dehydrochlorination reaction an interface growth controlled model of 1/3 order (F 1/3) appears to be the most suitable over a wide range of reaction. Dynamic thermogravimetry reveals two major steps in the temperature range 50–250C. The first step which corresponds to the loss of about 4 mols of H₂O, invariably follows second order kinetics (F₂). The second step which is predominantly a process of dehydrochlorination, generally fits mixed diffusion controlled models due to the overlapping with the dehydration process. There is an excellent agreement in results among the isothermal and non-isothermal methods of determining kinetic parameters.The authors are thankful to the Director, R. R. L. Bhubaneswar for his kind permission to publish this paper. One of the authors (SKM) is grateful to the Council of Scientific and Industrial Research, New Delhi, for the award of a Research Fellowship.     

The preparation of a series of ring-linked derivatives of [Fe2(η-C5H5)2(CO)2(μ-CO)2] starting from [Fe2η5,η5-C5H4CH(NMe3)CH(NMe2)C5H4}(CO)2(μ-CO)2]+ salts

The salts [Fe₂η⁵,η⁵-C₅H₄CH{NMe₃)CH(NMe₂)C₅H₄}(CO)₂(μ-CO)₂][X] (X = I or SO₃CF₃) are the synthetic precursors to a wide range of [Fe₂(η-C₅H₅)₂(CO)₂(μ-CO)₂] derivatives in which the two cyclopentadienyl ligands are joined by a two-carbon bridge.     

The reactions of [Fe2(η-Cp)2(CNAr)4] complexes with halogens and tin(II) halides

Summary [Fe₂(-Cp)₂(CNAr)₄] (2) (540-01, C₆H₄Me-2, C₆H₄Et-2, C₆H₃Me₂-2,4, C₆H₃Me₂-2,6, C₆H₃(Me)Et-2,6, C₆H₃Et₂-2,6 or C₆H₃ i-Pr₂-2,6) react with I₂ to give [Fe(-Cp)(CNAr)₂I], but with Br₂[Fe(-Cp) (CNAr)₃]⁺ salts are the only products; IBr gives a mixture of the two. With SnX₂ (X = F, Cl, Br or I) in refluxing n-butanol, (2) gives isolable [{Fe(-Cp)(CNAr)₂}₂SnX₂] only when the CNAr ligands have two ortho substituents, otherwise decomposition occurred. When X = F, [Fe(-Cp) (CNAr)₂SnF₃] was also obtained from this reaction. Attempts to prepare [Fe(-Cp)(CNAr)₂X] (X = Cl or Br) by reaction of (2) with HX in the presence of air gave rather unstable products which with SnX₂ formed [Fe(-C₅H₅)-(CNAr)₂SnX₃]. Similar compounds, [Fe(-Cp) (CNAr)₂ SnX₂I], were obtained from [Fe(-Cp)-(CNAr)₂I] and SnX₂ (X = Cl or Br but not I). All of these complexes are much less stable than their Fe(-Cp)(CO)₂ counterparts; all decompose in solution to [Fe(-Cp)(CNAr)₃]⁺ which then break down to unidentified species. X-ray diffraction studies show that in [Fe(-Cp)(CNC₆H₃-i-Pr₂-2,6)₂I] and [{Fe(-Cp)(CNC₆H₃Me₂-2,6)₂}₂SnBr₂] there is pseudo-octahedral coordination about Fe. In the latter there is also distorted tetrahedral coordination about Sn so that its structure is very similar to that of [{Fe(-Cp)(CO)₂}₂SnCl₂]. Spectroscopic studies show that in all complexes rotation of the aryl rings of the CNAr ligands cannot be slowed in solution, and that there is free rotation about all 540-02 bonds.