Hydride complexes of ruthenium derived from the heterolytic activation of dihydrogen by amidophosphine complexes

The reaction of 〚NPNH〛Ru(η³:η²-cyclooctadienyl) (1) (where 〚NPNH〛 = {PhNHSiMe₂CH₂P(Ph)CH₂SiMe₂NPh}), an organometallic mono-amide complex of ruthenium(II), with hydrogen gas (1–4 atm) generates three ruthenium hydride species: 〚NPNH〛RuH (2), 〚NPNH₂〛RuH₂(C₇H₈) (3) and 〚NPNH₂〛RuH₂ (4). All of these complexes result from hydrogenation of the cyclooctadienyl group; complexes 3 and 4 also undergo conversion of the amido linkage into a ruthenium hydride and an amine. Complexes 2 and 3 have been characterized both in solution by NMR spectroscopy and in the solid state by X-ray Diffraction and Infrared Spectroscopy. While 4 was fully characterized in solution by NMR spectroscopy, attempts to recrystallize this material yielded 2; the reaction of 2 with H₂ does not produce 4. The starting complex 1 acts as a catalyst precursor for the hydrogenation of imines such as benzylidene aniline; however, none of the isolated hydride species 2, 3 or 4 were active as catalyst precursors.     

‘A rendezvous with an old flame’: revisiting olefin hydrogenation with new rhodium and iridium catalysts

A novel tridentate hemilabile ligand 2 containing phosphine, imine and pyridyl donor groups has been prepared in analogy with the synthesis of the known related ligand 1. The reaction of 1 or 2 with 〚Rh(COE)₂Cl〛₂ resulted in the formation of the neutral complexes 〚Rh(L)Cl〛. By a method using 〚M(diene)Cl〛₂ as starting material, cationic complexes of the type 〚M(diene)(L)〛X were also obtained (M = Rh, diene = NBD, L = 1, 2; M = Ir, diene = COD, L = 1; X = BF₄, OTf). A comparative study of the catalytic activity of the new complexes towards the hydrogenation of various olefins has been reported. In particular, the catalysts of the type 〚Rh(L)Cl〛 are remarkably active when prepared in situ, especially for the reduction of hindered olefins.     

Dédoublement et détermination des excès énantiomériques des complexes de ruthéniumII hexacoordinés 〚Ru(bpy)2ppy〛+ et 〚Ru(bpy)2Quo〛+ (bpy = bipyridine,ppy = phénylpyridine,Quo = 8-quinolate) utilisés comme templates dans la construction de réseaux anioniques tridimensionnels

The bimetallic networks coordinated with oxalate bridges {〚M^IIM^III(C₂O₄)₃〛^–C⁺〛}_n form an important family of molecular magnets. The role of the cation C⁺ is fundamental for the nature of the obtained network (bi- or tridimensional). Thus, tridimensional polymers can be obtained in optically active forms using monocationic resolved templates such as 〚Ru(bpy)₂ppy〛⁺ 1 and 〚Ru(bpy)₂Quo〛⁺ 2. These cations were synthesized and resolved. A ¹H NMR technique based on the formation of diastereomeric salts obtained with optically active anion 〚ΔTrisphat〛^– {Trisphat = tris(tetrachlorobenzenediolato)phosphate(V)} was used to measure the enantiomeric excesses. To cite this article: M. Brissard et al., C. R. Chimie 5 (2002) 53–58     

Efficient hydroxylation of aromatic compounds catalyzed by an iron(II) complex with H2O2

A mononuclear iron(II) complex, Et₄N[Fe(C₁₀H₆NO₂)₃], coordinated by three 1‐nitroso‐2‐naphtholate ligands in a fac‐N₃O₃ geometry, was initiated to catalyze the direct hydroxylation of aromatic compounds to phenols in the presence of H₂O₂ under mild conditions. Various reaction parameters, including the catalyst dosage, temperature, mole ratio of H₂O₂ to benzene, reaction time and solvents which could affect the hydroxylation activity of the catalyst, were investigated systematically for benzene hydroxylation to obtain ideal benzene conversion and high phenol distribution. Under the optimum conditions, the benzene conversion was 10.2% and only phenol was detected. The catalyst was also found to be active towards hydroxylation of other aromatic compounds with high substrate conversions. The hydroxyl radical formed due to the reaction of the catalyst and H₂O₂ was determined to be the crucial active intermediate in the hydroxylation. A rational pathway for the formation of the hydroxyl radical was proposed and justified by the density functional theory calculations. Copyright © 2014 John Wiley & Sons, Ltd.     

Classical and non-classical iron hydrides: synthesis,NMR characterisation,theoretical investigation and X-ray crystal structure of the iron(IV) dihydride 〚Cp*Fe(dppe)(H)2〛+BF4–

Protonation of Cp*Fe(dppe)H (1; Cp* = η⁵-C₅Me₅, dppe = Ph₂PCH₂CH₂PPh₂) by HBF₄Et₂O at –80 °C in diethylether affords the dihydrogen complex 〚Cp*Fe(dppe)(η²-H₂)〛⁺BF₄^– (2⁺BF₄^–) in 90% yield. Its PF₆^– salt analogue (2⁺PF₆^–) is obtained in 94% yield by reaction between the 16-electron derivative 〚Cp*Fe(dppe)〛⁺PF₆^– (3⁺PF₆^–) with H₂ gas at –80 °C. The presence of a bound dihydrogen ligand in 2⁺ is indicated by a short T₁ minimum values consistent with a H–H distances of 0.98(1) Å. For the partially deuterated derivative 2⁺–d₁, the observed J_HD value of 27.0 Hz confirms the presence of the coordinated dihydrogen ligand, which displays an H–H separation of 0.97(1) Å, in complete agreement with the distance calculated using the T₁ static rotation model. Variable temperature NMR study shows the gradual, complete and irreversible transformation of the dihydrogen complex into its classical dihydride isomer trans-〚Cp*Fe(dppe)(H)₂〛⁺ (4⁺). Thermal solid state reaction (–20 °C, 48 h) of 2⁺BF₄^– gives quantitatively 4⁺BF₄^–, whereas 4⁺PF₆^– is obtained by simple contact of H₂ with a solution of 3⁺PF₆^– in THF at room temperature. The crystal structure of 4⁺BF₄^– has been determined and shows a transoid arrangement of hydride ligands, consistent with the formulation of 4⁺ as an iron(IV) dihydride. DFT calculations on both dihydride and dihydrogen isomers of 〚Cp*Fe(dppe)H₂〛⁺ indicate that 4⁺ is more stable than 2⁺ by 0.19 eV, while this energy difference is reversed in the case of 〚CpFe(dpe)H₂〛⁺ (dpe = H₂PCH₂CH₂PH₂). The preference for the dihydride form in the case of 〚Cp*Fe(dppe)H₂〛⁺ and of the dihydrogen one in the case of 〚CpFe(dpe)H₂〛⁺ is due to the larger π-donor and σ-acceptor abilities of the 〚Cp*Fe(dppe)〛⁺ fragment, as compared to the 〚CpFe(dpe)〛⁺ unit.     

Assembly and encapsulation of coordination tectons driven by hydrogen-bondingand space-filling

The synthesis and characterisation of 〚Fe(L^I)₃〛₂〚Fe(H₂O)₆〛(ClO₄)₆ (2), L^I = 1,10-phenanthroline-5,6-dione, is described. The crystal structure 2 is an unprecedented example of two-dimensional non-covalent array made up of 〚Fe(L^I)₃〛²⁺ species assembled by 〚Fe(H₂O)₆〛²⁺ cations encapsulated in pseudo-hexagonal cages. These cages are sustained by 12 hydrogen bonds established between the coordinated water molecules and the dione groups of six alternating Δ, Λ chiral 〚Fe(L^I)₃〛²⁺ moieties.     

Preparation,characterization and catalytic oxidation properties of tris[2‐(2‐pyridyl)benzimidazole]iron(II) complexes

Complexes [Fe(Hpbi)₃](ClO₄)₂ (1) and [Fe(Hpbi)₃](SbF₆)₂ (2) (Hpbi = 2‐(2‐pyridyl)benzimidazole) were prepared by a modified method and characterized by IR, ¹H and ¹³C NMR, mass spectrometry, electron paramagnetic resonance spectra and elemental analysis. The catalytic activities of 1 and 2 were evaluated for the oxidation of cyclohexene, cyclohexane, ethylbenzene and adamantane with tert‐butylhydroperoxide or H₂O₂ as oxidant, and the results were compared with the properties of their analogue [Fe(bpy)₃](SbF₆)₂ (3). Complexes 1 and 2 both afforded the ketonization product for the oxidation of ethylbenzene and the hydroxylation product for adamantane. Copyright © 2004 John Wiley & Sons, Ltd.     

Differentiation of planar chiral enantiomers of 〚Cp*M(2-alkyl-Phenoxo)〛 〚BF4〛 {M = Rh,Ir} by the trisphat anion

Precursor oxo-dienyl rhodium and iridium complexes 〚(η⁵-Cp*)M(η⁵-2-alkyl-oxodienyl)〛 〚BF₄〛 (2a–c) were prepared according to literature procedure. Addition of 〚n-Bu₄N〛 〚Δ-trisphat〛 (6) to a CD₂Cl₂ solution of these chiral derivatives has led to the NMR differentiation of the enantiomers. These results pave the way towards the preparation of enantiomerically pure o-quinone methide complexes.     

CH Photooxygenation of Alkyl Benzenes Catalyzed by Riboflavin Tetraacetate and a Non‐Heme Iron Catalyst

A mixture of the photocatalyst riboflavin tetraacetate (RFT) and the biomimetic non‐heme iron complex [Fe(TPA)(MeCN)₂](ClO₄)₂ (TPA=tris(2‐pyridylmethyl)amine) efficiently catalyzes the visible‐light‐driven aerobic oxidation of alkyl benzenes to ketones and carboxylic acids. An RFT‐catalyzed photocycle and the independent action of the iron complex as a catalyst for H₂O₂ disproportionation and alkyl benzene oxygenation ensure high yields and selectivities.     

Chemistry of iron complexes—III. X-ray diffraction,ESR and other spectral studies of new iron(II) and iron(III) complexes with tri-p-tolylarsine oxide

Reactions of iron(II) and iron(III) salts with tri-p-tolylarsine oxide(L) in suitable organic solvents yield complexes of formulas: (i) [FeL₂Cl₂(OH₂)₂] [FeCl₄].2H₂O, [FeL₂Br₂] [FeBr₄].2H₂O; (ii) [Fe(NCS)₃L₂].H₂O; (iii) [FeL(O₂ClO₂)₂(OH₂)] (ClO₄).0.25C₆H₆; (iv) [FeL₃I] [FeI₃].H₂O and (v) [Fe(CO)₃LI]I. Characterization has been done through elemental analyses, IR, far IR, ESR, and reflectance spectra, molar conductance, magnetic moments, t.g.a. and X-ray diffraction (powder) data. The species [FeL₂Cl₂(OH₂)₂]⁺, [FeL₂Br₂]⁺, [Fe(NCS)₃L₂], [FeL(O₂ClO₂)₂OH₂]⁺, [FeL₃I]⁺ and [Fe(CO)₃LI]⁺ have been assigned trans-octahedral, trans-square planar, trans-trigonal bipyramid, trans-octahedral, tetrahedral and cis-trigonal bipyramid structures respectively.     

Synthesis,structural and magnetic characterisation of MIL 36, Co(C7H10O4), a three-dimensional coordination polymer

Hydrothermal reaction of cobalt (II) salts with pimelate ions produces the new compound Co(C₇H₁₀O₄). It crystallises in the orthorhombic space group Pcca 〚a = 37.477 8(8) Å, b = 4.772 4(1) Å, c = 9.330 2(1) Å〛 and its structure was solved by single crystal X-ray diffraction. The neutral three-dimensional framework is built up from isolated cobalt tetrahedra bridged by pimelate ions. The connection involves the formation of two types of small channels. Magnetic measurements indicate a paramagnetic behaviour down to 20 K, the temperature at which magnetic susceptibility decreases due to the appearance of antiferromagnetic interactions. Co–CO₂–Co linkages give rise to infinite two-dimensional networks pillared by pimelate chains. ‘Super-superexchange’ via bridging carboxylate groups explains the low magnetic ordering temperature. Co(C₇H₁₀O₄), is denoted MIL-36 for Materials of Institut Lavoisier.     

Synthèse et propriétés biologiques des pyrazolo〚4,3-c〛triazolo〚4,3-a〛〚1,5〛benzodiazépines

The addition of carbon disulfide to 3(5)-N-〚methyl (ethyl)-2-aminophenyl amino-5(3)-phenylpyrazole 3 (4) afforded 10-methyl (ethyl)-3-phenylpyrazolo〚4,3-c〛 〚1,5〛 benzodiazepine-4-thione 7 (8). These compounds reacted with alkyl halides and acetylhydrazide or benzoylhydrazide, to afford new heterocyclic systems: pyrazolo 〚4,3-c〛 triazolo〚4,3-a〛-1,5-benzodiazepines 15–18. Biological properties of compounds 8, 9, 16 and 17 have been evaluated.     

Synthesis and structure of iron(III) complexes containing a quasi-crownether ring

A barium-iron(III) [BaFe(cr-salen)(py)₂](ClO₄)₃ (1) was prepared and an iron(III) complex [Fe(cr-salen)(py)₂]ClO₄ (2) complex was obtained by removing Ba²⁺ ion from the barium-iron(III) complexes with guanidinium sulfate. These complexes are in the high-spin state both in the solid state and in acetonitrile. Single crystals of [BaFe(cr-salen)(MeOH)₂]₂O(ClO₄)₄·2MeOH (3) were obtained by slow evaporation of a solution of (2) and Ba(ClO₄)₂, and the single crystal X-ray structure of (3) was determined: Crystal data for [BaFe(cr-salen)(MeOH)₂]₄O₂(ClO₄)₄·2MeOH: C₂₅H₃₆N₂O_17.5Cl₂BaFe, are: space group C2/c, Z=8, a=24.79(7) Å, b=16.11(6) Å, c=17.24(6) Å, V=6753(36) ų, R=0.133, R_w=0.154. The structure of the complex has a one order polymeric chain. An iron atom is located in a cavity of square pyramidal geometry and bridged by an oxygen atom of μ-oxo. A barium ion is sitted in a quasi-crownether ring and bridged by two perchlorate anions.     

Poly(4-vinylpyridine-co-divinylbenzene) supported iron(III) catalyst for selective oxidation of toluene to benzoic acid with H2O2

Poly(4-vinylpyridine-co-divinylbenzene) supported iron(III) catalysts were developed for the selective oxidation of toluene to benzoic acid in the presence of H₂O₂. The influence of the DVB content on the capacity of immobilized Fe(III) and on the catalytic activities of the polymeric complexes was investigated. The extent of Fe(III) uptake by the copolymers varied slightly with the concentration of DVB. The catalytic activities generally increase with increasing degree of crosslinker from 2 to 10% and decrease further with increasing the DVB content. Under the optimal conditions (80 °C, 6 h), the catalyst containing 10% DVB was found to be highly efficient in conversion of toluene to benzoic acid with 90% conversion and 96% selectivity.     

How well do we understand self-assembly algorithms? From prototype grid to polymers

Algorithms used for the assembly of metallosupramolecular constructs are simple and based upon well-established principles of coordination chemistry. The multinucleating ligand 3,6-bis(2-pyridyl)pyridazine forms a 〚2 × 2〛 grid with copper(I); the related ligand 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (dptz) is expected to behave in a similar manner with silver(I). However, instead of the expected grid, 〚Ag(dptz)₂〛⁺ solution species are formed. In the solid state, dinuclear 〚Ag₂(dptz)₂〛²⁺ and polymeric 〚{Ag(dptz-N,N’)(μ-dptz)}_n〛ⁿ⁺ complexes have been structurally characterised.     

Complexes triflates de l’uranium

Uranium triflate complexes. We review here the different preparations of uranium triflates that we have developed in the course of these last years in our laboratory. Protonation of 〚U〛–R and 〚U〛–NR₂ (R = alkyl) bonds with pyridinium triflate constitutes a general and efficient route towards triflate complexes. This method is very suitable for the preparation of organometallic compounds such as U(Cp)₃(OTf), U(Cp)₂(OTf)₂(py), U(Cp*)₂(OTf)₂, and U(Cot)(OTf)₂(py), which have been crystallographically characterised. The homoleptic species U(OTf)_n (n = 3, 4) are easily prepared by heating a mixture of uranium turnings or UH₃ in triflic acid. By adjusting the temperature to 120 or 180 °C, either U(OTf)₃ or U(OTf)₄ is isolated. Treatment of UO₃ with pure or aqueous solution of triflic acid leads to the non-solvated uranyl triflate UO₂(OTf)₂, which is more conveniently obtained by heating a suspension of UO₃ in triflic anhydride. This reactant is an excellent dehydrating agent and enables the preparation of UO₂(OTf)₂ and Ce(OTf)₄ from the hydrated starting materials.     

Effect of the hydrogen peroxide concentration in stereospecific oxidation of alkanes by models of non-heme oxygenases

The biomimetic oxidation of alkanes (cyclohexane, adamantane, cis-1,2-dimethylcyclohexane) with hydrogen peroxide catalyzed by Fe(II) complexes containing tetradentate nitrogen ligands (M = [Fe(bpmen)(MeCN)₂](ClO₄)₂ (bispicolyl-1,2-dimethylethylenediamine), [Fe(bpen)(MeCN)₂](ClO₄)₂ (bispicolylethylenediamine), and [Fe(tpcaH)(MeCN)₂]₂(ClO₄)₄ (tripyridylcarboxamide) is studied. The effects of the hydrogen peroxide concentration on the alcohol/ketone (A/K) ratio and on the regioselectivity of oxidation (3/2) are discovered. Rather high stereospecificity (RC = 96–99%) persisting at high hydrogen peroxide concentrations is hardly consistent with the participation of the HO^. radical, inferred from the rather low regioselectivity and low A/K ratio observed under these conditions. The molecular mechanism of oxygen transfer from hydrogen peroxide, which was earlier proved reliably for low concentrations of hydrogen peroxide ([H₂O₂]/[M] ? 10), can be applied to high peroxide concentrations ([H₂O₂]/[M] > 10) if a new ferryl species containing two equivalents of the oxidant is assumed to be involved in the process. This assumption is confirmed by the direct stereospecific formation of alkyl hydroperoxide from alkane at a high concentration of hydrogen peroxide.     

Fe/Al-PILC催化C_3H_6选择性还原NO的实验研究

采用浸渍法制备了负载于铝柱撑黏土的铁基催化剂(Fe/Al-PILC),在固定床反应器上测试其催化C3H6选择性还原NO的性能。通过N2吸附-脱附、X射线衍射(XRD)、H2的程序升温还原(H2-TPR)、紫外可见光谱(Uv-vis)、吡啶吸附红外光谱(Py-FTIR)等手段对催化剂的物理化学性质进行表征。结果表明,9Fe/Al-PILC在400-550℃能够还原98%以上的NO,而且SO2和水蒸气对其催化性能的影响很小。XRD、N2吸附-脱附表征结果表明,Fe/Al-PILC催化剂中铁氧化物高度分散在载体表面,催化剂有较大的比表面积和孔容。H2-TPR结果表明,催化剂的活性主要由Fe_2O_3物相的还原性能决定。Uv-vis结果表明,催化剂的活性与铁氧低聚物种FexOy呈正相关性。Py-FTIR结果表明,催化剂表面同时存在Lewis酸和Brnsted酸,L酸性位是NO和C3H6反应的主要催化活性中心。     

Synthesis,crystal structures and magnetic properties of two iron (II) tris(pyridyl)phosphine selenides complexes

We reported the synthesis of tris(pyridyl)phosphine selenide (TppSe) and tris(4-methylpyridin-2-yl)phosphine selenide (MeTppSe), which were prepared by a simple and straightforward one-pot method with red phosphorus in a KOH/DMSO suspension, and treatment of resulted phosphines with selenium in hot toluene. These compounds were characterized by mass spectroscopy, ¹H, ¹³C and ³¹P NMR spectroscopies and the structure of MeTppSe was characterised by a single-crystal X-ray diffraction. Furthermore, The reactions of selenides with Fe(ClO₄)₂·6H₂O afforded two new iron(II) mononuclear metal complexes [Fe(TppSe)₂][ClO₄]₂·3DMF (1) and [Fe(MeTppSe)₂][ClO₄]₂·2DMF (2). Detailed structural analyses and magnetic susceptibility measurements confirm no spin transition from low-spin to the high-spin state between 2 and 300 K in two iron(II) complexes.