Direct synthesis of Fe(III) immobilized Zr‐based metal–organic framework for aerobic oxidation reaction

A Zr‐based metal–organic framework with bipyridine units (UiO‐67) has been utilized for the immobilization of catalytically active iron species via a post‐synthetic metalation method. UiO‐67 bipyridine MOF was synthesized through a simple solvothermal method and was shown to have a UiO‐type structure. Post‐synthetic metalation of UiO‐67 MOF was performed for the immobilization of the catalytically active FeCl₃. FT‐IR and EDX element map suggested that FeCl₃ is coordinately bonded to the UiO‐67 bipyridine framework. The synthesized UiO‐67‐FeCl₃ catalyst was used for the aerobic oxidation of alcohols and benzylic compounds in the presence of molecular oxygen. In addition, the UiO‐67‐FeCl₃ catalyst can be reused as a solid heterogeneous catalyst without compromising its activity and selectivity.     

A diphenylphosphinoethane-functionalized polystyrene resin-supported Pd(0) complex as an effective catalyst for copper-free Sonogashira coupling reactions under aerobic conditions

A polymer-supported palladium(0) diphenylphosphinoethane complex was found to be a highly active catalyst for the copper-free Sonogashira coupling reaction of aryl iodides with terminal alkynes, giving excellent yields of products (85-98%) under aerobic conditions.     

Ruthenium(II), rhodium(III) and iridium(III) based effective catalysts for hydrogenation under aerobic conditions

The new cationic mononuclear complexes [(η⁶-arene)Ru(Ph-BIAN)Cl]BF₄ [η⁶-arene = benzene (1), p-cymene (2)], [(η⁵-C₅H₅)Ru(Ph-BIAN)PPh₃]BF₄ (3) and [(η⁵-C₅Me₅)M(Ph-BIAN)Cl]BF₄ [M = Rh (4), Ir (5)] incorporating 1,2-bis(phenylimino)acenaphthene (Ph-BIAN) are reported. The complexes have been fully characterized by analytical and spectral (IR, NMR, FAB-MS, electronic and emission) studies. The molecular structure of the representative iridium complex [(η⁵-C₅Me₅)Ir(Ph-BIAN)Cl]BF₄ has been determined crystallographically. Complexes 1–5 effectively catalyze the reduction of terephthaldehyde in the presence of HCOOH/CH₃COONa in water under aerobic conditions and, among these complexes the rhodium complex [(η⁵-C₅Me₅)Rh(Ph-BIAN)Cl]BF₄ (4) displays the most effective catalytic activity.     

Determination of Fe(II), Fe(III) and Fetotal in thermal water by ion chromatography spectrophotometry (IC-Vis)

Determination of iron speciation in water is one of the major challenges in environmental analytical chemistry. Here, we present and discuss a method for sampling and analysis of dissolved Fe(II), Fe(III), and Fe_total concentrations in natural thermal water covering a wide range of temperature, pH, chemical composition, and redox conditions. Various methods were tried in the collection, preservation, and storage of natural thermal water samples for the Fe(II) and Fe(III) determinations, yet the resultant Fe speciation determined was often found to be significantly affected by the methodology applied. Due to difficulties in preserving accurate Fe speciation in natural samples for later laboratory analysis, a field-deployed on-site method using ion-chromatography and spectrophotometry was developed and tested. The IC-Vis method takes advantage of ion chromatographic separation of Fe(II) and Fe(III), followed by post-column colour reaction and spectrophotometric detection, thus allowing analysis of Fe(II) and Fe(III) in a single 15-minute run. Additionally, Fe_total can be determined after sample oxidation. The analytical detection limits are ~2 µg L^?1 (LOD) using 200–1000 µL injection volumes and depend on the blank and reagent quality. The power of this method relies on the capability to directly determine a wide range of absolute and relative concentrations of Fe(II) and Fe(III) in the field. The field-deployed IC-Vis method was applied for the determination of Fe(II) and Fe(III) concentrations in natural thermal water with discharge temperatures ranging from 12°C to 95°C, pH between 2.46 and 9.75, and Fe_total concentrations ranging from a few μg L^?c up to 8.3 mg L^?1.     

Polymer-supported palladium perfluorooctanesulfonate [Pd(OPf)2]: A recyclable and ligand-free palladium catalyst for copper-free Sonogashira coupling reaction in water under aerobic conditions

Amberlyst A-21, a kind of well-known and cheap polymeric material, was treated with palladium perfluorooctanesulfonate [Pd(OPf)₂] giving a reagent with a palladium loading of 1.94 (wt%). The polymer-supported fluorous palladium catalyzes the highly efficient Sonogashira coupling reaction in water. The reactions can be performed under copper- and ligand-free conditions in an air atmosphere. The palladium catalyst is easily separated and can be reused several times without a significant loss of catalytic activity.     

A copper- and solvent-free coupling of acid chlorides with terminal alkynes catalyzed by a polystyrene-supported palladium(0) complex under aerobic conditions

A polystyrene-supported palladium(0) complex [PS-dpp-Pd(0)] is an efficient catalyst for the copper- and solvent-free acylation of terminal alkynes with different acid chlorides in the presence of triethylamine as base, giving the corresponding ynones in good yields.     

A simple and efficient one-pot synthesis of 1,4-dihydropyridines using heterogeneous catalyst under solvent-free conditions

One-pot condensation of β-dicarbonyl compounds with aldehydes and ammonium acetate in the presence of HClO₄–SiO₂ at 80 °C under solvent-free conditions with good to excellent yields. The catalyst is easily prepared, stable, reusable and efficiently used under reaction conditions.     

Nano tetraimine Pd(0) complex as an efficient catalyst for phosphine‐free Suzuki reaction in water and copper‐free Sonogashira reaction under aerobic conditions

A nano tetraimine Pd(0) complex catalyst was successfully used as an efficient heterogeneous catalyst for the phosphine‐free palladium‐catalysed Suzuki coupling reaction in water at 80 °C. This nano tetraimine Pd(0) complex was also used for copper‐free Sonogashira reaction in dimethylformamide at 100 °C. The catalyst was easily recovered from the reaction mixture by centrifugation and reused for at least six cycles without any significant loss in its catalytic activity. Analysis of the reaction mixture using inductively coupled plasma analysis showed that leaching of palladium from the catalyst was negligible. The reactions can be performed efficiently for aryl iodides, bromides and also chlorides. Copyright © 2016 John Wiley & Sons, Ltd.     

Iron‐catalyzed cross‐coupling reaction: Heterogeneous palladium and copper‐free Heck and Sonogashira cross‐coupling reactions catalyzed by a reusable Fe(III) complex

An interesting silica‐supported iron catalyst was successfully prepared and demonstrated as an efficient heterogeneous catalyst for cross‐coupling reactions of aryl halides. The as‐prepared nanocatalyst was well characterized and found to be highly efficient in Heck reaction under mild and sustainable conditions (water as solvent at 80 °C in short reaction time). Furthermore, the obtained catalyst was used as an efficient, inexpensive and green heterogeneous catalyst for Sonogashira cross‐coupling reactions of various aryl iodides and provided the corresponding products with moderate to good yields. This phosphine, copper and palladium‐free catalyst was simply recovered from the reaction mixture and recycled five times without substantial decrease in its catalytic activity.     

Complexes of Fe(III) and Ga(III) Derived from the Cyclic 6- and 7-Membered Hydroxamic Acids Found in Mixed Siderophores

Six- and seven-membered cyclic hydroxamic acids are found as terminal binding units in different families of siderophores, including exochelins and mycobactins. The simplest models of these preorganized chelating ligands were known, but their coordination chemistry with Fe³⁺, the target metal ion of siderophores, had never been reported. Four complexes were synthesized and studied: two Fe³⁺ complexes, one with the six-membered ring hydroxamate PIPO⁻ and one with the seven-membered ring hydroxamate AZEPO⁻, and the two corresponding Ga³⁺ complexes. X-ray diffraction studies showed that the interligand repulsion energies were better minimized in the case of the AZEPO⁻ complexes whatever the metal cation considered, and that the Fe−O bond distances were shorter in [Fe(AZEPO)₃] by comparison with [Fe(PIPO)₃].     

Iron Forms Fe(II) and Fe(III) Determination in Pre-Roman Iron Age Archaeological Pottery as a New Tool in Archaeometry

This article presents studies on iron speciation in the pottery obtained from archaeological sites. The determination of iron forms Fe(II) and Fe(III) has been provided by a very simple test that is available for routine analysis involving the technique of molecular absorption spectrophotometry (UV–Vis) in the acid leachable fraction of pottery. The elemental composition of the acid leachable fraction has been determined by inductively coupled plasma optical emission spectrometry (ICP-OES). Additionally, the total concentration of the selected elements has been determined by X-ray fluorescence spectrometry with energy dispersion (EDXRF). The results of the iron forms’ determinations in archaeological pottery samples have been applied in the archaeometric studies on the potential recognition of the pottery production technology, definitely going beyond the traditional analysis of the pottery colour.     

Naked-eye detection of Cu (II) and Fe (III) based on a Schiff Base Ruthenium complex with nicotinohydrazide

A cyclometalated ruthenium (II) complex 1 [(Ru (Phen)₂(Pbznh)]⁺ PF₆⁻ (Phen = 1,10-phenanthroline and Pbznh = N-(4-(pyridine-2-yl)benzylidene) nicotinohydrazide) with nicotinohydrazide as a functional group was synthesized and characterized. Changes of its absorption spectra and color induced by Cu²⁺ and Fe³⁺ were systematic investigated. The results demonstrated that complex 1 could be served as a colorimetric probe to fast, selective and sensitive detection of Cu²⁺ and Fe³⁺ both in acetonitrile and filter paper based strips. Upon addition of Cu²⁺ and Fe³⁺ to solution of probe 1 , solution color changed from pink to colorless and light yellow respectively, and their corresponding detection limit were calculated to be 3.26 × 10⁻⁸ M and 3.12 × 10⁻⁷ M. Moreover, color of test papers with 1 changed from pink to colorless/yellow when Cu²⁺/Fe³⁺ were dropwise added. Therefore, it can be used as a desirable ‘naked-eye’ indicator candidate for Cu²⁺ and Fe³⁺.     

Facile route to synthesis of functionalised poly(methylalkoxy)siloxane under mild and aerobic conditions in the presence of platinum catalysts

A facile and high yield method of synthesis of novel and functional poly(methylalkoxy) siloxanes is reported. The Si–H groups of poly(methylhydrogen) siloxanes (PMHS) were treated with various simple (primary, secondary, tertiary) alcohols (1a–10a) in the presence of platinum based catalysts (Speier’s and Karstedt’s catalysts). Also oxyethylene, aldehyde, epoxide, halogen and allyl grafted polysiloxane were smoothly and quantitatively prepared by the alcoholysis between linear siloxanes polymer and functional alcohols (11a–20a) with use of Karstedt’s catalysts. It is found that alcoholysis reaction in the presence of the Karstedt’s catalyst proceed faster than Speier’s catalyst .In addition, the rate of alcoholysis reaction is dependent on amount of the catalyst and reaction temperature. The polymers prepared were characterized by IR, NMR spectroscopy and GPC analysis.     

Synthesis and characterization of soft–hard stereoblock polybutadiene with Fe(2‐EHA)3/Al(i‐Bu)3/DEP catalyst system

Stereoblock polybutadiene (PBD) composed of amorphous equibinary cis?1,4/1,2 PBD (e‐PBD, soft) and crystalline syndiotactic 1,2‐PBD (s‐1,2‐PBD, hard) segments is synthesized through one‐pot sequential polymerization with iron(III)2‐ethylhexanoate/triisobutylaluminum/diethyl phosphate [Fe(2‐EHA)₃/Al(i‐Bu)₃/DEP] catalyst system. The first‐stage polymerization of 1,3‐butadiene (BD) is carried out at a low [Al]/[Fe] ratio to give amorphous e‐PBD block, and sequentially, the in situ addition of excessive Al(i‐Bu)₃ and BD to the living polymerization system give rise to a second crystalline s‐1,2‐PBD block. The length of each block is controllable by adjusting cocatalyst and monomer feed ratio. The syndiotactic pentad content is in the range of 63.8–76.6% and increases with the length of s‐1,2‐PBD block. The copolymer exhibits glass transition temperature (T_g) around ?40 °C and melting point (T_m) around 168 °C originating from e‐PBD and s‐1,2‐PBD blocks, respectively. The incompatibility between s‐1,2‐PBD and e‐PBD blocks as well as the crystallization of s‐1,2‐PBD block induce the microphase separation in stereoblock PBD. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1182–1188     

Fe3O4/MIL‐101(Fe) nanocomposite as an efficient and recyclable catalyst for Strecker reaction

A highly porous metal‐organic framework, MIL‐101(Fe), was prepared by a solvothermal method in the presence of amino‐modified Fe₃O₄@SiO₂ nanoparticles, in order to achieve Fe₃O₄/MIL‐101(Fe) nanocomposite, which was characterized by XRD, FT‐IR, SEM, TEM, BET, and VSM. This hybrid magnetic nanocomposite was employed as heterogeneous catalyst for α‐amino nitriles synthesis through three‐component condensation reaction of aldehydes (ketones), amines, and trimethylsilyl cyanide in EtOH, at room temperature. The recoverability and reusability was admitted for the heterogeneous magnetic catalyst; no significant reduction of catalytic activity was observed even after five consecutive reaction cycles.     

A practical innovative method for highly selective oxidation of alkenes and alkanes using Fe (III) and Mn (III) porphyrins supported onto multi‐wall carbon nanotubes as reusable heterogeneous catalysts

Functionalized multi‐walled carbon nanotubes were used for covalent immobilization of meso‐tetrakis(4‐carboxyphenyl) porphyrinatoiron (III) chloride [Fe (TCPP)Cl] and meso‐tetrakis(4‐carboxyphenyl) porphyrinatomanganese (III) acetate [Mn (TCPP)OAc]. The full characterization of the hybrid porphyrinic nanomaterials, by Fourier transform‐infrared and UV–Vis spectroscopy, transmission electron microscopy, thermogravimetry and flame atomic absorption spectrometry is described. The oxidation of alkenes and alkanes with molecular oxygen as green oxidant in the presence of Mn‐ and Fe‐catalysts has been studied in a comparative manner. The Fe‐catalyst was shown to have higher catalytic activity compared with the Mn‐catalyst. In addition, both separable solid catalysts can be recovered and reused at least 10 times along with good yields.     

Xanthan sulfuric acid: An efficient and biodegradable solid acid catalyst for the synthesis of bis(indolyl)methanes under solvent-free conditions

Xanthan sulfuric acid (XSA) is found to be an efficient catalyst for the electrophilic substitution reaction of indole with aromatic aldehydes to afford the corresponding bis(indolyl)methanes at room temperature under solvent-free conditions. The catalyst was characterized for the first time with the help of powder XRD, SEM–EDX and DSC–TGA. The attractive features of this green, new methodology are excellent yield of products, clean reaction profile, reusability of the catalyst, energy sustainable protocol, simple experimental and easier work-up procedures.     

Tungstophosphoric acid nanoparticles supported on polyamic acid: A mild and recoverable heterogeneous catalyst for the selective synthesis of mono and bulky bis(1,8-dioxooctahydroxanthene)s under solvent-free conditions

A series of 1,8-dioxooctahydroxanthene derivatives and some crowded bis(1,8-dioxooctahdroxanthene) were selectively synthesized using tungstophosphoric acid nanoparticles supported on polyamic acid (TPA/PAA) as a new catalyst in solvent-free conditions. The high purity products were isolated and catalyst was easily separated in simple work-up and was recycled several times without loss of reactivity under the described reaction conditions. The reaction is characterized by short reaction time, high efficiency and environmentally friendly reaction conditions.     

Adsorption of Fe(III) from Aqueous Medium onto Glycine-Modified Chitosan Resin: Equilibrium and Kinetic Studies

The adsorption of Fe(III) onto glycine-modified chitosan (G@Chs) resin has been investigated. The parameters studied include the effects of pH, contact time, and initial metal ion concentrations by batch method. The optimal pH for the adsorption of Fe(III) was found to be 2.5. The results obtained from equilibrium adsorption studies are fitted in various adsorption models such as Langmuir and Freundlich, and each model parameter were evaluated. Kinetics and thermodynamic parameters of the adsorption process were also investigated. The maximum uptake was found to be 0.9 mmol g^?1 at 25°C.     

Synthesis of bis(indolyl)methanes under catalyst-free and solvent-free conditions

Abstract

Condensation of indole with aromatic aldehydes has been carried out without using any catalyst and solvent to give bis(indolyl)methanes.