Phosphine Groups Research Articles

Living 3,4-Isoselective (Co)polymerization of Biobased β-Farnesene Catalyzed by Phosphine-Functionalized Fluorenyl Rare-Earth Metal Catalysts

With an objective to reduce petrochemical dependency, synthesis of biobased polymers from renewable feedstocks has been widely investigated. In this study, we report that living and highly 3,4-isoselective polymerization of the biobased monomer β-farnesene (100% 3,4-, >99% mmmm) can be realized at room temperature using a phosphine-functionalized fluorenyl-ligated yttrium catalytic system with ultrahigh activity. Detailed investigations suggested that the coordinated phosphine group plays a pivotal role in the high regio- and stereoselectivity of 1-Y-catalyzed β-farnesene polymerization, and the density functional density (DFT) calculation offered important insights into the 3,4-isoselectivity. Additionally, block copolymers featuring rigid 3,4-isospecific polyisoprene blocks and amorphous 3,4-isospecific polyfarnesene blocks were successfully prepared. The morphology and mechanical properties of these elastomeric copolymers were studied by using atomic force microscopy and stress–strain experiments, respectively.

Improving the dyeing and fastness performance of molecular triphenodioxazine on wool and nylon fabrics

Three novel triphenodioxazine acid dyes (phosphorous-containing acid dyes; PAD2–4) modified by phenophosphazine with non-planar conformation were designed and synthesized. Their dyeing and fastness performance on wool and nylon fabrics were discussed in comparison with the performances of traditional triphenodioxazine (TPDO) dyes such as C.I. Direct Blue 106 and C.I. Reactive Blue 198. The excellent dyeing and fastness performance of PAD2–4 on the wool and nylon fabrics were analyzed using DFT calculations. The phosphinic group of these PADs is thought to play a key role in the improvement of the exhaustion dyeing performance; the easier offset face-to-face stacking arrangement was attributed to the overwhelming increase of the rubbing fastness owing to the stronger Van der Waals interactions, as calculated using DFT. A design strategy that includes the introduction of an extra-weak acid group and a zigzagged rigid planar component into the TPDO matrix offers insight into improving the poor exhaustion and fastness performance of traditional TPDOs.

Piperazine/Alkene-Containing Phosphoramide Oligomer for the Intumescent Flame Retardation of EPDM Rubber

Ethylene propylene diene monomer (EPDM) rubber is highly flammable, facing potential fire hazard when it is used as electric cable sheaths, automobile parts, etc. In this work, aiming to reduce fire hazard of EPDM rubber, a piperazine/alkene-containing phosphoramide oligomer poly (2-butene-1,4-dione piperazine fumaroyl phenylphosphonate) (PPFPP) was synthesized and used as charring agent to fabricate intumescent flame retardant with ammonium polyphosphate (APP). When 20 wt% APP/PPFPP (weight ratio: 3:1) was incorporated into EPDM, the flame-retarded EPDM achieved the UL-94 V-0 rating and the limiting oxygen index (LOI) of 27.0%, significantly superior to flame-retarded EPDM consisting of controlled flame retardant PPSPP without alkene and PPFA without phenyl phosphine. In cone calorimeter test, flame retardant consisting of 6.25 wt% PPFPP and 18.75 wt% APP strongly reduced the peak of heat release rate (PHRR) and the peak of smoke production rate (PSPR) of EDPM, diminished approximately by 72% and 60%, respectively. In the case of meeting flame retardancy, mechanical property of flame-retarded EPDM maintained at a high level. Different measurements confirmed that the flame-retardant mechanism of PPFPP is attributed to two aspects. The first one is ascribed to the char-forming action of PPFPP in the presence of alkene and piperazine, playing a barrier role in condensed phase; the second one is due to the gaseous action of phenyl phosphine groups originating from the pyrolysis of PPFPP. In summary, the combination of piperazine and alkene with phenyl phosphine may fabricate an efficient charring agent for the intumescent flame retardation for EPDM.

Phosphinate MOFs Formed from Tetratopic Ligands as Proton-Conductive Materials.

Metal-organic frameworks (MOFs) are attracting attention as potential proton conductors. There are two main advantages of MOFs in this application: the possibility of rational design and tuning of the properties and clear conduction pathways given by their crystalline structure. We hereby present two new MOF structures, ICR-10 and ICR-11, based on tetratopic phosphinate ligands. The structures of both MOFs were determined by 3D electron diffraction. They both crystallize in the P3̅ space group and contain arrays of parallel linear pores lined with hydrophilic noncoordinated phosphinate groups. This, together with the adsorbed water molecules, facilitates proton transfer via the Grotthuss mechanism, leading to a proton conductivity of up to 4.26 × 10-4 S cm-1 for ICR-11. The presented study demonstrates the high potential of phosphinate MOFs for the fabrication of proton conductors.

Grafted mesoporous silicas for radionuclide uptake: Radiolytic stability under electron irradiation

Materials developed for radionuclide adsorption need to resist harsh conditions, i.e. be robust against ionizing radiation. In this work, we evaluated the degradation of mesoporous silicas (SBA-15) grafted with hydroxypiridinone, acetamide phosphonate and propionamide phosphonate ligands under electron irradiation. The ligands contained amide and/or phosphinic acid functional groups, which made them able to bind to actinides. Degradation of the grafted ligand was assessed by identifying and quantifying the gas produced under irradiation using gas chromatography, as well as characterizing the grafted ligands before and after irradiation by means of FT-IR, XPS and TGA techniques. Irradiation led to the degradation of amide functional groups and to the production of amine and carboxylic acid groups. Corresponding reaction mechanisms were proposed. The sorption behavior of the grafted SBA-15 materials for thorium was also studied. SBA-15 materials grafted with acetamide phosphonate and propionamide phosphonate ligands were shown to be able to adsorb thorium. The propionamide phosphate ligand was the most efficient, with an equilibrium sorption capacity of 95 mg g−1. This capacity remained stable up to a 1 MGy irradiation dose and underwent a 20% decrease after 4 MGy of irradiation. Therefore, this material is potentially interesting for the treatment of liquid outflows contaminated by actinides produced in nuclear facilities.

Di- and tri-block copolymers from the sequential living anionic copolymerization a phosphaalkene with styrene

The living anionic polymerization of the phosphaalkene, MesP=CPh 2 ( PA ), affords a series of poly(methylenephosphine) (PMP) homo- and block co-polymers with styrene (S). Specifically, PMP m ( m = 30, 40, 50, 50), PS n – b –PMP m ( n , m = 100,29; 100,50; 50,30; 51, 62) and PMP m – b –PS 2 n – b –PMP m (2 n , m = 100,4; 200,8; 400,16; 400,24) have been prepared and characterized. Analysis by GPC-MALS-V showed that all samples were monodisperse, displayed narrow dispersities ( Đ = 1.03–1.29), and generally had molecular weights within ±(2–26%) of those targeted from the monomer-to-initiator ratios. All homo- and co-polymers displayed a single T g in their DSC chromatograms with the transition temperature for the copolymers being in between those of the corresponding homopolymers. These transitions appear to be dependent on both the copolymer composition and the corresponding chain lengths. • Living anionic copolymerization of a phosphaalkene with styrene is accomplished. • Diblock and triblock copolymers contain functional phosphine groups. • Phosphine homopolymers have high glass transition temperatures (ca. 150 °C).

Comparing the Electronic Structure of Iron, Cobalt, and Nickel Compounds That Feature a Phosphine-Substituted Bis(imino)pyridine Chelate

It was recently discovered that (Ph2PPrPDI)Mn (PDI = pyridine diimine) exists as a superposition of low-spin Mn(II) that is supported by a PDI dianion and intermediate-spin Mn(II) that is antiferromagnetically coupled to a triplet PDI dianion, a finding that encouraged the synthesis and electronic structure evaluation of late first row metal variants that feature the same chelate. The addition of Ph2PPrPDI to FeBr2 resulted in bromide dissociation and the formation of [(Ph2PPrPDI)FeBr][Br]. Reduction of this precursor using excess sodium amalgam afforded (Ph2PPrPDI)Fe, which possesses an Fe(II) center that is supported by a dianionic PDI ligand. Similarly, reduction of a premixed solution of Ph2PPrPDI and CoCl2 yielded the cobalt analog, (Ph2PPrPDI)Co. EPR spectroscopy and density functional theory calculations revealed that this compound features a high-spin Co(I) center that is antiferromagnetically coupled to a PDI radical anion. The addition of Ph2PPrPDI to Ni(COD)2 resulted in ligand displacement and the formation of (Ph2PPrPDI)Ni, which was found to possess a pendent phosphine group. Single-crystal X-ray diffraction, CASSCF calculations, and EPR spectroscopy indicate that (Ph2PPrPDI)Ni is best described as having a Ni(II)-PDI2- configuration. The electronic differences between these compounds are highlighted, and a computational analysis of Ph2PPrPDI denticity has revealed the thermodynamic penalties associated with phosphine dissociation from 5-coordinate (Ph2PPrPDI)Mn, (Ph2PPrPDI)Fe, and (Ph2PPrPDI)Co.

Trihexyl(tetradecyl)phosphonium bis-2,4,4-(trimethylpentyl)phosphinate micellar behavior in the extraction of Ag(I) from acidic nitrate media

The distribution of Ag(I) between acidic aqueous phase (HNO3) and organic phases, composed of trihexyl(tetradecyl)phosphonium bis-(2,4,4-trimethylpentyl)phosphinate (Cyphos® IL 104) diluted in kerosene or kerosene/1-decanol, has been studied. In order to elucidate the interactions in solution and the chemical equilibria responsible for Ag(I) extraction by Cyphos® IL 104, ionic conductivity, dynamic viscosity, and interfacial tension measurements, determination of water and nitric acid extraction were performed, and the organic phases were characterized by infrared spectroscopy (ATR-FTIR). Ag(I) is extracted by Cyphos® IL 104 with high affinity, even under slightly acidic conditions (close to 100% at pH 5). The linear relationship between the logarithm of the distribution ratio of Ag(I) (D) and the logarithm of Cyphos® IL 104 concentration exhibits a slope greater than the stoichiometry expected (1:1), demonstrating an atypical extraction equilibrium. The change in the physicochemical properties as a function of Cyphos® IL 104 concentration permits to deduce the formation of reverse micelles or aggregates in organic phases at the critical micellar concentration CMC = 0.001 mol L-1. The ATR-FTIR characterization showed that Ag(I) was extracted by the phosphinate group of Cyphos® IL 104 with the transfer of water and nitric acid. A thorough analysis of these data indicates a similar mechanism to solvation, and the reverse micelles (or agglomerates) are involved in Ag(I) extraction.

Sulforaphane and Its Bifunctional Analogs: Synthesis and Biological Activity.

For decades, various plants have been studied as sources of biologically active compounds. Compounds with anticancer and antimicrobial properties are the most frequently desired. Cruciferous plants, including Brussels sprouts, broccoli, and wasabi, have a special role in the research studies. Studies have shown that consumption of these plants reduce the risk of lung, breast, and prostate cancers. The high chemopreventive and anticancer potential of cruciferous plants results from the presence of a large amount of glucosinolates, which, under the influence of myrosinase, undergo an enzymatic transformation to biologically active isothiocyanates (ITCs). Natural isothiocyanates, such as benzyl isothiocyanate, phenethyl isothiocyanate, or the best-tested sulforaphane, possess anticancer activity at all stages of the carcinogenesis process, show antibacterial activity, and are used in organic synthesis. Methods of synthesis of sulforaphane, as well as its natural or synthetic bifunctional analogues with sulfinyl, sulfanyl, sulfonyl, phosphonate, phosphinate, phosphine oxide, carbonyl, ester, carboxamide, ether, or additional isothiocyanate functional groups, and with the unbranched alkyl chain containing 2–6 carbon atoms, are discussed in this review. The biological activity of these compounds are also reported. In the first section, glucosinolates, isothiocyanates, and mercapturic acids (their metabolites) are briefly characterized. Additionally, the most studied anticancer and antibacterial mechanisms of ITC actions are discussed.

Bioinspired Di-Fe Complexes: Correlating Structure and Proton Transfer over Four Oxidation States.

Metalloproteins with active sites containing di-Fe cores exhibit diverse chemical reactivity that is linked to the precise transfer of protons and electrons which directly involve the di-Fe units. The redox conversions are commonly corroborated by spectroscopic methods, but the associated structural changes are often difficult to assess, particularly those related to proton movements. This report describes the development of di-Fe complexes in which the movements of protons and electrons are pinpointed during the stepwise oxidation of a di-FeII species to one with an FeIIIFeIV core. Complex formation was promoted using the phosphinic amido tripodal ligand [poat]3- (N,N',N″-[nitrilotris(ethane-2,1-diyl)]tris(P,P-diphenylphosphinic amido)) that provided dynamic coordination spheres that assisted in regulating both electron and proton transfer processes. Oxidation of an [FeII-(μ-OH)-FeIII] complex led to the corresponding di-FeIII species containing a hydroxido bridge that was not stable at room temperature and converted to a species containing an oxido bridging ligand and protonation of one phosphinic amido group to form [Hpoat]2-. Deprotonation led to a new species with an [FeIII-(μ-O)-FeIII] core that could be further oxidized to its FeIIIFeIV analogue. Reactions with phenols suggest homolytic cleavage of the O-H bond to give products that are consistent with the initial formation of a phenoxyl radical─spectroscopic studies indicated that the electron is transferred to the FeIV center, and the proton is initially transferred to the more sterically hindered oxido ligand but then relocates to [poat]3-. These findings offer new mechanistic insights related to the stability of and the reactions performed by di-Fe enzymes.

Changes in ligand coordination mode induce bimetallic C-C coupling pathways.

Carbon-carbon coupling is one of the most powerful tools in the organic synthesis arsenal. Known methodologies primarily exploit monometallic Pd0/PdII catalytic mechanisms to give new C-C bonds. Bimetallic C-C coupling mechanisms that involve a PdI/PdII redox cycle, remain underexplored. Thus, a detailed mechnaistic understanding is imperative for the development of new bimetallic catalysts. Previously, a PdII-Me dimer (1) supported by L1, which has phosphine and 1-azaallyl donor groups, underwent reductive elimination to give ethane, a PdI dimer, a PdII monometallic complex, and Pd black. Herein, a comprehensive experimental and computational study of the reactivity of 1 is presented, which reveals that the versatile coordination chemistry of L1 promotes bimetallic C-C bond formation. The phosphine 1-azaallyl ligand adopts various bridging modes to maintain the bimetallic structure throughout the C-C bond forming mechanism, which involves intramolecular methyl transfer and 1,1-reductive elimination from one of the palladium atoms. The minor byproduct, methane, likely forms through a monometallic intermediate that is sensitive to solvent C-H activation. Overall, the capacity of L1 to adopt different coordination modes promotes the bimetallic C-C coupling channel through pathways that are unattainable with statically-coordinated ligands.

Thermally stable zinc hydride catalyst for hydrosilylation of CO2 to silyl formate at atmospheric pressure.

Neutral zinc complexes supported by H[PNNO], a diaminophenolate ligand bearing a pendant phosphine group, were synthesized and characterized. The phosphine arm adopts two different configurations in solution and prevents aggregation. The monomeric zinc hydride complex is stable at elevated temperatures up to 125 °C and reacts readily with CO2 to afford a zinc formate complex. The zinc hydride is active for CO2 hydrosilylation at atmospheric CO2 pressure and is selective for CO2 reduction to the silyl-formate product.

Flotation extraction of tin from tailings of sulfide-tin ore dressing using thermomorphic polymer

The possibility of using a thermomorphic polymer with a phosphine group as a collecting reagent for the selective concentration of tin during flotation enrichment of sulfide-tin tails was first investigated in the work. A detailed description of the experimental scheme of flotation concentration of sulfide-tin ore tailings and the reagent mode are given. The main mineral of tin is cassiterite, highly brittle and inclined to sludging, which leads to large losses of tin with tails; the granulometric composition of the initial tails of the Solnechnyi mining and processing plant has showed that 50% of the sample is represented by size grade of –0.04 mm. The output of a slimy product of –20 μm is 20% with a tin content of 0.46% (according to chemical analysis). This product is one of the sources of tin losses (up to 33.5%) in the flotation concentration process and requires additional technological solutions. It has been shown that the use of selective concentration of the +20 μm class using a thermomorphic polymer (TMPF) for flotation of tin ores allows not only to reduce the loss of tin with thin classes, but also significantly increase the flotation rate of cassiterite and technological parameters when beneficiating mature tailings of tin-sulfide ore processing. The main tin flotation using TMPF results in obtaining a rough tin concentrate I with a content of 0.55% Sn and extracting 49% of the operation. Rough tin concentrate II with a content of 0.38% Sn and 42% recovery was obtained by reextraction using TMPF. The total recovery of tin in the combined rough tin concentrate amounted to 90.71% of the operation. Subsequent purification of the obtained concentrate and gravity enrichment on the table concentrator will make it possible to obtain the concentrates richer in tin content required for their further processing. Further research will be aimed at developing scientifically based technological solutions to improve the quality of rough tin concentrate and extracting tin from the sludge product –0.02 microns using new reagent compositions. The study has been implemented at the expense of the Russian Science Foundation grant (project No. 17-17-01292).

Silica gels grafting with upper rim tetraphosphorylated tetrahydroxy(thia)calixarenes. Europium(III) sorption

Sequential treatment of silica gel with tetrachlorosilane and cone-shaped tetraphosphorylated tetrahydroxy(thia)calixarenes yielded porous organo-inorganic sorbents, the surface of which is covered by spatially ordered phosphonate, phosphinate and phosphine oxide groups capable of co-operative binding of metal cations. Sorption of europium(III) by the modified silica gels was studied.

Computational study of the boraformylation of allenes catalyzed by copper complexes

The bifunctionalization of allenes is a powerful tool with potential for generating many pharmaceuticals, natural products, and biologically active molecules. In this study, theoretical calculations based on the density functional theory (DFT) were used to investigate the mechanism involved in the boraformylation of propadiene catalyzed by an active copper complex bearing a bulky phosphine group as an ancillary ligand. The process was characterized by a four-step mechanism, in which the transition state with the highest energy is that one associated with the substrate addition to the active catalyst, while the largest energy barrier is found to the β-elimination step. In addition, the non-covalent interaction (NCI) analysis performed over all the transition states unveiled the importance of non-covalent interactions to the entire reaction mechanism.

Indium-Catalyzed CO2/Epoxide Copolymerization: Enhancing Reactivity with a Hemilabile Phosphine Donor.

Group 13 metal complexes have emerged as powerful catalysts for transforming CO2 into added-value products. However, direct comparisons of reactivity between Al, Ga, and In catalysts are rare. We report aluminum (1), gallium (2), and indium (3) complexes supported by a half-salen H[PNNO] ligand with a pendent phosphine donor and investigate their activity as catalysts for the copolymerization of CO2 and cyclohexene oxide. In solution, the P-donor is dissociated for the Al and Ga complexes while for the In complex it exhibits hemilabile behavior. The indium complex shows higher conversion and selectivity than the Al or Ga analogues. The mechanism of the reaction was studied by NMR and FTIR spectroscopy experiments as well as structural characterization of off-cycle catalytic intermediate indium trichloride complex [(PNNO)InCl3][TBA] (4). This study highlights the impact of a hemilabile phosphine group on group 13 metals and provides a detailed analysis of the initiation step in CO2/epoxide copolymerization reactions.

Synthesis of New Thiourea-Metal Complexes with Promising Anticancer Properties.

In this work, two thiourea ligands bearing a phosphine group in one arm and in the other a phenyl group (T2) or 3,5-di-CF3 substituted phenyl ring (T1) have been prepared and their coordination to Au and Ag has been studied. A different behavior is observed for gold complexes, a linear geometry with coordination only to the phosphorus atom or an equilibrium between the linear and three-coordinated species is present, whereas for silver complexes the coordination of the ligand as P^S chelate is found. The thiourea ligands and their complexes were explored against different cancer cell lines (HeLa, A549, and Jurkat). The thiourea ligands do not exhibit relevant cytotoxicity in the tested cell lines and the coordination of a metal triggers excellent cytotoxic values in all cases. In general, data showed that gold complexes are more cytotoxic than the silver compounds with T1, in particular the complexes [AuT1(PPh3)]OTf, the bis(thiourea) [Au(T1)2]OTf and the gold-thiolate species [Au(SR)T1]. In contrast, with T2 better results are obtained with silver species [AgT1(PPh3)]OTf and the [Ag(T1)2]OTf. The role played by the ancillary ligand bound to the metal is important since it strongly affects the cytotoxic activity, being the bis(thiourea) complex the most active species. This study demonstrates that metal complexes derived from thiourea can be biologically active and these compounds are promising leads for further development as potential anticancer agents.

Self-Adaptable Tropos Catalysts.

ConspectusBiological systems have often served as inspiration for the design of synthetic catalysts. The lock and key analogy put forward by Emil Fischer in 1894 to explain the high substrate specificity of enzymes has been used as a general guiding principle aimed at enhancing the selectivity of chemical processes by optimizing attractive and repulsive interactions in molecular recognition events. However, although a perfect fit of a substrate to a catalytic site may enhance the selectivity of a specific catalytic reaction, it inevitably leads to a narrow substrate scope, excluding substrates with different sizes and shapes from efficient binding. An ideal catalyst should instead be able to accommodate a wide range of substrates—it has indeed been recognized that enzymes also are often highly promiscuous as a result of their ability to change their conformation and shape in response to a substrate—and preferentially be useful in various types of processes. In biological adaptation, the process by which species become fitted to new environments is crucial for their ability to cope with changing environmental conditions. With this in mind, we have been exploring catalytic systems that can adapt their size and shape to the environment with the goal of developing synthetic catalysts with wide scope.In this Account, we describe our studies aimed at elucidating how metal catalysts with flexible structural units adapt their binding pockets to the reacting substrate. Throughout our studies, ligands equipped with tropos biaryl units have been explored, and the palladium-catalyzed allylic alkylation reaction has been used as a suitable probe to study the adaptability of the catalytic systems. The conformations of catalytically active metal complexes under different conditions have been studied by both experimental and theoretical methods. By the design of ligands incorporating two flexible units, the symmetry properties of metal complexes could be used to facilitate conformational analysis and thereby provide valuable insight into the structures of complexes involved in the catalytic cycle. The importance of flexibility was convincingly demonstrated when a phosphine group in a privileged ligand that is well-known for its versatility in a number of processes was exchanged for a tropos biaryl phosphite unit: the result was a truly self-adaptive ligand with dramatically increased scope.

Metal-Free Bond Activation by Carboranyl Diphosphines.

We report metal-free bond activation by the carboranyl diphosphine 1-PtBu2-2-PiPr2-C2B10H10. This main group element system contains basic binding sites and possesses the ability to cycle through two-electron redox states. The reported reactions with selected main group hydrides and alcohols occur via the formal oxidation of the phosphine groups and concomitant reduction of the boron cage. These transformations, which are driven by the cooperation between the electron-donating exohedral substituents and the electron-accepting cluster, differ from those of "regular" phosphines and are reminiscent of oxidative addition to transition metal centers, thus representing a new approach to metal-free bond activation.

Rational construction of a novel ratiometric far-red fluorescent probe with excellent water solubility for sensing mitochondrial peroxynitrite

Peroxynitrite (ONOO−) is closely associated with various pathophysiological processes and mainly produced within the mitochondria. Therefore, developing an efficient method for mitochondrial ONOO− detection is crucial for better understanding of its functions. In view of the advantages of ratiometric fluorescent probes and far-red/NIR fluorescent probes, a kind of novel mitochondrion-targeting ratiometric far-red fluorescent probe (ANI-DP) was reasonably constructed by employing isophorone derivative as fluorescence group, diphenyl phosphinate as response group, and pyridinium cation as mitochondria-targetable group. Probe ANI-DP displayed a distinctive ratiometric fluorescence response toward ONOO− with a red-shifted emision in far-red to NIR region owing to the cleavage of a phosphinate group and change of intramolecular charge transfer (ICT) efficiency induced by ONOO−. In 100 % aqueous solution, probe ANI-DP was capable of quantitatively detecting ONOO− levels ranging from 0 to 10 μM with a low detection limit of 13.3 nM, and showed high specificity for ONOO− over other biological relevant substances. Besides, it featured large Stokes shift (202 nm), high photostability, low cytotoxicity as well as good mitochondria targetable ability. Encouraged by the outstanding properties described above, it was successfully applicated for ratiometric fluorescence imaging of ONOO− in mitochondria of living cells as well as visualization of ONOO− in zebrafish, which indicated that it holds great potential for revealing the functions of ONOO− in living biosystems.