Water-soluble Phosphine Ligands Research Articles

Anticancer Water-Soluble Organoruthenium Complexes: Synthesis and Preclinical Evaluation.

The synthesis, characterisation, and evaluation of the in vitro cytotoxicity of five maleonitriledithiolate‐based ruthenium metal complexes bearing various phosphine ligands towards two ovarian cancer cell lines (A2780 and A2780cisR), one non‐small‐cell lung cancer cell line (H460) and one normal prostate cell line (PNT2) are presented herein. These 18‐electron complexes were designed with four water‐soluble phosphine ligands to increase the water‐solubility character of the corresponding electron‐deficient ruthenium complex which showed great in vitro promises, and triphenylphosphine for comparison. The complexes with triphenylphosphine‐3,3′,3′′‐trisulfonic acid and triphenylphosphine present similar cytotoxicity compared to the 16‐electron precursor, with equal cytotoxicity to both A2780 and A2780cisR. Hints at the mechanism of action suggest an apoptotic pathway based on reactive oxygen species (ROS) production. No toxicity was observed in preliminary in vivo pilot studies for these two complexes in subcutaneous A2780 and A2780cisR xenograft models, with some evidence of tumour growth delay.

Aqueous biphasic hydroformylation of olefins: From classical phosphine-containing systems to emerging strategies based on water-soluble nonphosphine ligands

ABSTRACTThis review provides an overview of recent developments in the area of aqueous biphasic hydroformylation of higher olefins using metal catalysts and surfactants, cosolvents, thermoregulated ligands, cyclodextrins, and most importantly emerging water-soluble nonphosphine ligands. Water-soluble phosphine ligands have been widely explored for aqueous biphasic hydroformylation; however, phosphines are generally expensive and are prone to oxidation hence the recent interest in exploring other ligands. Various approaches have been used to introduce hydrophilicity to the ligands. The catalytic activity of monometallic and heterobimetallic systems containing nonphosphine ligands in aqueous biphasic media is emphasized in this review.

Palladium nanoparticles stabilized by phosphine ligand for aqueous phase room temperature suzuki-Miyaura coupling

Water soluble phosphine ligand triphenylphosphine-3,3′,3″-trisulfonic acid trisodium salt (TPPTS) was used as the stabilizer as well as the activator to the palladium nanoparticles, which showed a high catalytic performance for aqueous phase Suzuki-Miyaura coupling reaction at room temperature.

Investigation of 1,3,5-Triaza-7-phosphaadamantane-Stabilized Silver Nanoparticles as Catalysts for the Hydration of Benzonitriles and Acetone Cyanohydrin

A straightforward synthesis of water-soluble silver nanoparticles stabilized by PTA (1,3,5-triaza-7-phosphaadamantane, a water-soluble phosphine ligand) ligands was developed. The nanoparticles were thoroughly characterized by ultraviolet–visible spectroscopy, 31P nuclear magnetic resonance spectroscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. The effectiveness of the Ag–PTA nanoparticles as catalysts for the hydration of nitriles to amides in water under mild conditions was explored using a series of substituted benzonitriles and cyanohydrins. In comparison to all previously investigated homogeneous catalysts, the Ag–PTA system excels at cyanohydrin hydration, including acetone cyanohydrin hydration. Cyanohydrins are in equilibrium with small amounts of cyanide, and experiments revealed that the Ag–PTA nanoparticles disassemble in the presence of cyanide. The catalyst solution, which is proposed to contain a soluble Ag(CN)n1–n complex (with n likely equal to 2), remained unpoisoned even in the presence of 10 equiv of cyanide. It is suggested that no cyanide poisoning occurs because the Ag(I) complex is labile. Overall, the Ag–PTA catalyst system (a) is not poisoned by cyanide, (b) catalyzes hydration reactions under mild conditions (in air and at relatively low temperatures), (c) is easily synthesized from cheap starting materials, and (d) can hydrate heteroaromatics in good yields. The recognition of the importance of labile metal cyanide bonding represents an important step forward in catalyst design for improving the catalytic hydration of acetone cyanohydrin.

Catalytic hydrogenation of levulinic acid in aqueous phase

The hydrogenation of levulinic acid (LA) yielding γ-valerolactone (GVL) has been examined in aqueous solution using various water soluble phosphine ligands in combination with the metal precursors [Ru(acac)3] and [RuCl3]. Using catalyst loadings of only 0.2 mol%, GVL could be obtained in yields up to 99% conversion and 97% selectivity along with a maximum turnover frequency of 200molGVLmolRu−1h−1 within 5 h, using 3,3′,3′′-phosphinidynetris(benzenesulfonic acid) trisodium salt (TPPTS) and Ru(acac)3 as catalytic system. In addition, a ruthenium–phosphine complex immobilized on the amphiphilic copolymer PS-PEG was examined under the same conditions and gave 90% conversion of LA in 24 h.

Photocatalytic Water Reduction and Study of the Formation of FeIFe0 Species in Diiron Catalyst Sytems

Noble-metal-free systems with bio-inspired diiron dithiolate mimics of the [FeFe]-hydrogenase active site, namely, [(μ-pdt)Fe(2) (CO)(5) L] [pdt=propanedithiolate; L=P(CH(2) OH)(3) (1), P(CH(3) )(3) (2)], as water reduction catalysts with xanthene dyes as photosensitizers and triethylamine as a sacrificial electron donor were studied for visible-light-driven water reduction to hydrogen. These systems display good catalytic activities with the efficiencies in hydrogen evolution of up to 226 turnovers for 1, if Eosin Y was used as the photosensitizer in an environmentally benign solvent (EtOH/H(2) O) after 15 h of irradiation (λ>450 nm) under optimal conditions. Under all of the conditions adopted, 1 that has a water soluble phosphine ligand, P(CH(2) OH)(3) displayed a higher efficiency than 2, which bears a PMe(3) ligand. The photoinduced electron transfer in the systems was studied using fluorescence, transient absorption, time-resolved UV/Vis, and in situ electron paramagnetic resonance (EPR) spectroscopy. A new electron-transfer mechanism is proposed for hydrogen evolution by these iron-based photocatalytic systems.

Hydrogen Storage and Delivery: The Carbon Dioxide – Formic Acid Couple

Carbon dioxide and the carbonates, the available natural C1 sources, can be easily hydrogenated into formic acid and formates in water; the rate of this reduction strongly depends on the pH of the solution. This reaction is catalysed by ruthenium(II) pre-catalyst complexes with a large variety of water-soluble phosphine ligands; high conversions and turnover numbers have been realised. Although ruthenium(II) is predominant in these reactions, the iron(II) - tris[(2-diphenylphosphino)-ethyl]phosphine (PP3) complex is also active, showing a new perspective to use abundant and inexpensive iron-based compounds in the CO2 reduction. In the catalytic hydrogenation cycles the in situ formed metal hydride complexes play a key role, their structures with several other intermediates have been proven by multinuclear NMR spectroscopy. In the other hand safe and convenient hydrogen storage and supply is the fundamental question for the further development of the hydrogen economy; and carbon dioxide has been recognised to be a viable H2 vector. Formic acid--containing 4.4 weight % of H2, that is 53 g hydrogen per litre--is suitable for H2 storage; we have shown that in aqueous solutions it can be selectively decomposed into CO-free (CO < 10 ppm) CO2 and H2. The reaction takes place under mild experimental conditions and it is able to generate high pressure H2 (up to 600 bar). The cleavage of HCOOH is catalysed by several hydrophilic Ru(II) phosphine complexes (meta-trisulfonated triphenylphosphine, mTPPTS, being the most efficient one), either in homogeneous systems or as immobilised catalysts. We have also shown that the iron(II)--hydrido tris[(2-diphenylphosphino)ethyl]phosphine complex catalyses with an exceptionally high rate and efficiency (turnover frequency, TOF = 9425 h(-1)mol(-1); turnover number, TON = 92400) the formic acid cleavage, in environmentally friendly propylene carbonate solution, opening the way to use cheap, non-noble metal based catalysts for this reaction, too.

The Suzuki Reaction in Aqueous Media Promoted by P, N Ligands

The synthesis and structure of palladium complexes of trisubstituted PTA derivatives, PTAR3, are described. Water-soluble phosphine ligands 1,3,5-triaza-7-phosphaadmantane (PTA), tris(aminomethyl)phosphine trihydrobromide, tri(aminomethyl) phosphine, 3,7-dimethyl-1,5,7-triaza-3-phosphabicyclo[3,3,1]nonane (RO-PTA), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA), lithium 1,3,5-triaza-7-phosphaadamantane-6-carboxylate (PTA-CO2Li), 2,4,6-triphenyl-1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane, and 2,4,6-triphenyl-1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane were used as ligands for palladium catalyzed Suzuki reactions in aqueous media. RO-PTA in combination with palladium acetate or palladium chloride was the most active catalyst for Suzuki cross coupling of aryl bromides and phenylboronic acid at 80 °C in 1:1 water:acetonitrile. The activity of Pd(II) complexes of RO-PTA is comparable to PPh2(m-C6H4SO3Na) (TPPMS) and P(m-C6H4SO3Na)3 (TPPTS) and less active than tri(4,6-dimethyl-3-sulfonatophenyl)phosphine trisodium salt (TXPTS). Activated, deactivated, and sterically hindered aryl bromides were examined, with yields ranging from 50% to 90% in 6 h with 5% palladium precatalyst loading. X-ray crystal structures of (RO-PTA)PdCl2, (PTAR3)2PdCl2 (R = Ph, p-tert-butylC6H5), and PTAR3 (R = p-tert-butylC6H5) are reported.

Synthesis of non-symmetrically sulphonated phosphine sulphonate based Pd(ii) catalyst salts for olefin polymerisation reactions

Direct sulphonation of 2-(diphenylphosphino)benzenesulphonic acid was extensively studied. The non-symmetrically functionalised reaction products obtained, related to the widely applied water soluble phosphine ligands m,m,m-TPPTS and m,m-TPPDS, display chelating κ(2)-(P,O)-coordination to Pd(II) metal centres. Phase transfer reaction of rac-o,m-TPPDS as the potassium salt with 18-crown-6 and complexation to Pd(II) gives the novel anionic catalyst precursor [K(18-crown-6)](2)[κ(2)(P,O){rac-o,m-TPPDS}PdMeCl] suitable for olefin polymerisation reactions. Ethene homo- and co-polymerisation reactions with polar functionalised olefins were investigated with this anionic phosphine sulphonate Pd(II)-based pre-catalyst salt.

Influence of water-soluble sulfonated phosphine ligands on ruthenium catalyzed generation of hydrogen from formic acid

Hydrogen can be generated from formic acid in aqueous phase homogeneous catalytic reactions using ruthenium catalysts with water-soluble phosphine ligands. A comparison of tri-, di-, and mono-sulfonato triphenylphosphine, disulfonato diphenyl-alkyl-phosphines (Ph2PR; R=Me, n-Bu, Cyp), and monosulfonato phenyl-dialkyl-phosphines (PhPR2; R=Me, Cyp) is described. Using two equivalents of water-soluble phosphine per ruthenium ion, significant turnover frequencies are observed for the decomposition of formic acid. The influence of basicity, water solubility (related to the structures and behavior in aqueous solution), electronic properties, and steric effects of the phosphines on the rate of the hydrogen generation are investigated.

Anticancer Therapeutics That Target Selenoenzymes: Synthesis, Characterization, in vitro Cytotoxicity, and Thioredoxin Reductase Inhibition of a Series of Gold(I) Complexes Containing Hydrophilic Phosphine Ligands

Gold(I) complexes bearing water-soluble phosphine ligands, including 1,3,5-triaza-7-phosphaadamantane (PTA), 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane (DAPTA), and sodium triphenylphosphine trisulfonate (TPPTS), in combination with thionate ligands, were screened for their antiproliferative activities against human ovarian cancer cell lines A2780 either sensitive or resistant to cisplatin. In addition, the compounds were screened for their inhibition of mammalian thioredoxin reductases (TrxR), enzymes that are overexpressed in many tumor cells and contribute to drug resistance. The gold(I)-phosphine complexes efficiently inhibited cytosolic and mitochondrial TrxRs at concentrations that did not affect the related oxidoreductase glutathione reductase (GR). Additional complementary information on the enzyme metallation process and potential gold binding sites was obtained through the application of a specific biochemical assay using a thiol-tagging reagent, BIAM (biotin-conjugated iodoacetamide).

Synthesis and characterization of water-soluble palladium(II)-functionalized diphosphine complexes

Water-soluble functionalized bis(phosphine) ligands L ( a– h) of the general formula CH 2(CH 2PR 2) 2, where for a: R = (CH 2) 6OH; b– g: R = (CH 2) n P(O)(OEt) 2, n = 2–6 and n = 8; h: R = (CH 2) 3NH 2 ( Scheme 1), have been prepared photochemically by hydrophosphination of the corresponding 1-alkenes with H 2P(CH 2) 3PH 2. Water-soluble palladium complexes cis-[Pd( L)(OAc) 2] ( 1– 8) were obtained by the reaction of Pd(OAc) 2 with the ligands a– h in a 1:1 mixture of dichloromethane:acetonitrile. The water-soluble phosphine ligands and their palladium complexes were characterized by IR, 1H and 31P NMR. A crystallographic study of complex 1 shows that the Pd(II) ion has a square planar coordination sphere in which the acetate ligands and the diphosphine ligand deviate by less than 0.12 Å from ideal planar.

Exploring the Water-Soluble Phosphine Ligand as the Environmentally Friendly Stabilizer for Electroless Nickel Plating

Phosphine (R3P) compounds being a typical type of coordination ligand used in homogeneous catalysis are known to possess a tunable affinity with the nickel atom. As such, it deserves to be studied ...

Insertion of CO2, Ketones, and Aldehydes into the C−Li Bond of 1,3,5-Triaza-7-phosphaadamantan-6-yllithium

The synthesis and structures of a series of new water-soluble phosphine ligands based on 1,3,5-triaza-7-phosphaadamantane (PTA) are described. Insertion of aldehydes or ketones into the C-Li bond of 1,3,5-triaza-7-phosphaadamantan-6-yllithium (PTA-Li) resulted in the formation of a series of slightly water-soluble beta-phosphino alcohols (PTA-CRR'OH, R = C6H5, C(6)H(4)OCH(3), ferrocenyl; R' = H, C(6)H(5), C(6)H(4)OCH(3)) derived from the heterocyclic phosphine PTA. Insertion of CO(2) yielded the highly water-soluble carboxylate PTA-CO(2)Li, S(2)5 degrees approximately 800 g/L. The compounds have been fully characterized in the solid state by X-ray crystallography and in solution by multinuclear NMR spectroscopy. The addition of PTA-Li to symmetric ketones results in a racemic mixture of PTA-CR(2)OH ligands with a single resonance in the (31)P{(1)H} NMR spectrum between -95 and -97 ppm. The addition of PTA-Li to aldehydes results in a mixture of diasteromeric compounds, PTA-CHROH, with two (31)P{(1)H} NMR resonances between -100 and -106 ppm. Three (eta(6)-arene)RuCl(2)(PTA-CRR'OH) complexes of these ligands were synthesized and characterized, with the ligands binding in a kappa1 coordination mode. All the ligands and ruthenium complexes are slightly soluble in water with S25 degrees = 3.9-11.1 g/L for the PTA-CRR'OH ligands and S(25) degrees = 3.3-14.1 g/L for the (eta(6)-arene)RuCl(2)(PTA-CRR'OH) complexes.

Homogenous Catalysis with Gold: Efficient Hydration of Phenylacetylene in Aqueous Media

A variety of gold(I) complexes containing the water-soluble phosphine ligands TPPMS, TPPDS, and TPPTS (mono-, di-, and tri-sulfonated triphenylphosphine, respectively) were tested as catalysts for the hydration of phenylacetylene in aqueous media. The gold(I) alkynyl complexes [AuC⋮CR(TPPTS)] (where R = tBu and 3-thiophenyl) give the highest ever reported turnover frequencies (1000 and 1060 h-1, respectively) for the hydration of phenylacetylene under optimum conditions (0.1 mol % catalyst loading, 10 mol % H2SO4, 1 h reflux in 5:1 MeOH/H2O). The hydration of phenylacetylene can also be carried out using only water and reaction medium, which allows recycling of the gold catalyst without significant drop of activity for at least three cycles. DFT calculations were used to compare relative energies of possible intermediates involved in the catalytic cycle.

Water-soluble and water-stable Gold(I), Gold(II) and Gold(III) phosphine complexes: The early years

This article briefly reviews the still rather limited knowledge of the chemistry, structures, reactions and applications of gold complexes containing water-soluble phosphine ligands sorted by gold oxidation state.

Triarylphosphine-Stabilized Platinum Nanoparticles in Three-Dimensional Nanostructured Films as Active Electrocatalysts

Ligand-stabilized platinum nanoparticles (Pt NPs) can be used to build well-defined three-dimensional (3-D) nanostructured electrodes for better control of the catalyst architecture in proton exchange membrane fuel cells (PEMFCs). Platinum NPs of 1.7 +/- 0.5 nm diameter stabilized by the water-soluble phosphine ligand, tris(4-phosphonatophenyl)phosphine (TPPTP, P(4-C6H4PO3H2)3), were prepared by ethylene glycol reduction of chloroplatinic acid and subsequent treatment of the isolated nanoparticles with TPPTP. The isolated TPPTP-stabilized Pt NPs were characterized by multinuclear magnetic resonance spectroscopy (31P and 195Pt NMR), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS). The negatively charged TPPTP-Pt NPs were electrostatically deposited onto a glassy carbon electrode (GCE) modified with protonated 4-aminophenyl functional groups (APh). Multilayers were assembled via electrostatic layer-by-layer deposition with cationic poly(allylamine HCl) (PAH). These multilayer films are active for the key hydrogen fuel cell reactions, hydrogen oxidation (anode) and oxygen reduction (cathode). Using a rotating disk electrode configuration, fully mass-transport limited kinetics for hydrogen oxidation was obtained after 3 layers of TPPTP-Pt NPs with a total Pt loading of 4.2 microg/cm2. Complete reduction of oxygen by four electrons was achieved with 4 layers of TPPTP-Pt NPs and a total Pt loading of 5.6 microg/cm2. A maximum current density for oxygen reduction was reached with these films after 5 layers resulting in a mass-specific activity, i(m), of 0.11 A/mg(Pt) at 0.9 V. These films feature a high electrocatalytic activity and can be used to create systematic changes in the catalyst chemistry and architecture to provide insight for building better electrocatalysts.

Suzuki reaction of cyclopenta[ d][1,2]oxazine in aqueous solvent with water-soluble phosphine ligand

A convenient and facile modification of cyclopenta[ d][1,2]oxazines through Suzuki cross-coupling reaction by use of water-soluble phosphine ligand was accomplished. In aqueous solvent, 7-iodocyclopenta[ d][1,2]oxazines readily afford the corresponding 7-arylcyclopenta[ d][1,2]oxazines in moderate to excellent yields.

Enhanced Reductive Elimination of Dialkylgold(III) Complexes in Water

Abstract Neutral and cationic dimethyl- or diethylgold(III) complexes having a water-soluble phosphine ligand, AuR2XL and [AuR2L2]X (R = Me or Et; X = Br or I; L = TPPTS, TPPMS, THMP, or DHMPE), are prepared. Reductive elimination involving C–C bond formation at Au(III) in water is faster than those in organic solvents.

Catalytic Insertion Polymerization of Norbornene in Miniemulsion

The catalytic insertion polymerization of norbornene (NB) was implemented under miniemulsion conditions. Using sodium dodecyl sulfate (SDS) as surfactant and hexadecane as hydrophobe, the insertion polymerization was initiated by multicomponent catalysts generated in situ by reacting allylpalladium chloride dimer, [(eta(3)-allyl)Pd(Cl)](2), with a desired phosphine ligand and then activating the resulting procatalyst with a salt of noncoordinating anion, typically the lithium salt of tetrakis(pentafluorophenyl)borate (Li[B(C6F5)(4)]center dot 2.5Et(2)O). By choosing either an organo-soluble (tricyclohoxylphosphine) or a water-soluble phosphine ligand (tris(3-sulfonatophenyl)phosphine sodium salt), two palladium procatalysts I and II exhibiting different solubilities in water were generated and then used to polymerize NB in miniemulsion. After activation, both I and H displayed high activity and led to stable PNB latexes with good particle size control throughout the course of the reaction. Stable polynorbornene latexes with a relatively broad particle size distribution were produced. The number-average particle diameter is often below 100 nm. The nature of the surfactant and the effect of changing the concentrations of activating agent, procatalyst, and hydrophobe on the polymerization kinetics, latex stability, and particle size were investigated.