Regeneration of platinum-metal-based catalysts with carboxyphosphines as extractants

Separation of platinum-metal-based homogeneous catalysts was achieved by their conversion to complexes of functionalized phosphines of the general formulae R_3-n P[(CH₂) _x CO₂H)] _n , R = Me, Et, Ph,n = 1, 2, 3,x = 1, 2, and [(HO₂CCH₂)PCH₂]₂, followed by extraction of the complexes into aqueous phase. This approach to regeneration of platinum metals from reaction mixtures after carrying out homogeneously catalyzed reactions was demonstrated on 11 examples of various types of reactions with Ru, Rh, Pd, Os, Ir and Pt compounds as catalysts.     

Effect of Coordination Modes of HL Ligand on the Molecular Architecture of Its Transition Metal Complexes (HL = 5-Methyl-2-Phenyl-4-[(2-<Emphasis Type="Italic">o</Emphasis>-Tolylamino)-Phenylmethylene]pyrazol-3(2H)-one)

Abstract  Two Ag⁺ complexes [Ag(HL)₂(PF₆)] (1) and [(AgL) _n  · n(CH₂Cl₂) · n(0.5H₂O)] (2) (HL = 5-methyl-2-phenyl-4-[(2-o-tolylamino)-phenylmethylene]pyrazol-3(2H)-one) were synthesized and structurally characterized by EA analysis, IR spectra and X-ray crystallography. The result shows that two expected coordination modes (Modes I and III in Scheme 1) of the HL ligand, can be observed in its Ag⁺ complexes, while not in other transition metal ions (Ni²⁺, Co²⁺ or Cu²⁺) complexes whether deprotonation or not for the HL ligand. Graphical Abstract  Three possible coordination modes (Modes I, II or III in Scheme 1) of the selected HL (HL = 5-methyl-2-phenyl-4-[(2-o-tolylamino)-phenylmethylene]pyrazol-3(2H)-one) ligand, can be adopted, in which Modes I and III can be observed in its two Ag⁺ complexes [Ag(HL)₂(PF₆)](1) and [(AgL) _n  · n(CH₂Cl₂) · n(0.5H₂O)] (2), while Mode II just observed in its transition metal ions (Cu²⁺, Ni²⁺, or Co²⁺) complexes, resulting from the deprotonatd form of the HL ligand and the coordination characters of transition metal ions.      

Synthesis of Ruthenium Hydride Complexes Containing beta‐Aminophosphine Ligands Derived from Amino Acids and their use in the H2‐Hydrogenation of Ketones and Imines

The new complexes RuHCl(PPh₂CH₂CHRNH₂)₂ and RuHCl(PPh₂CH₂CHRNH₂)(R‐ binap), R=H (Pgly), R=Me [(R)‐Pala] were prepared by the substitution of the PPh₃ ligands in RuHCl(PPh₃)₃ or RuHCl(PPh₃)[(R)‐binap] with beta‐aminophosphines derived from amino acids. The complex trans‐RuHCl(Pgly)[(R)‐binap] has been characterized by X‐ray crystallography. The complex trans‐RuHCl[(S)‐Ppro]₂ where (S)‐Ppro is derived from proline was also prepared and characterized by X‐ray crystallography. These were used as catalyst precursors in the presence of a base (KOPr‐i or KOBu‐t) for the hydrogenation of various ketones and imines to the respective alcohols and amines with H₂ gas (1–11 atm) at room temperature. Acetophenone was hydrogenated to (S)‐1‐phenylethanol in low ee (up to 40%) when catalyzed by the enantiomerically pure complexes. These complexes are especially active in the hydrogenation of sterically congested and electronically deactivated ketones and imines and are selective for the hydrogenation of CO bonds over CC bonds.     

The Hydroamination of methyl acrylates with amines over zeolites

H-form zeolites, H-FAU and H-BEA have been studied as heterogeneous catalysts for the hydroamination. They catalyzed the reaction of methyl acrylate with aniline to give N-[2-(methoxycarbonyl)ethyl]aniline (1) as a main product. H-BEA and H-FAU zeolites efficiently catalyzed the hydroamination to afford anti-Markovnikov adduct as a main product. The conversion of aniline around 55–85% was achieved within 18 h over H-BEA and H-FAU zeolites with SiO₂/Al₂O₃ molar ratio of 25–30; however, the formation of N,N-bis[2-(methoxycarbonyl)ethyl]aniline (2) as a product of double addition of methyl acrylate to aniline has also been observed as a by-product over H-BEA and H-FAU catalysts. The influences of the reaction parameters such as temperature and catalyst amount, and type of α,β-unsaturated esters and amines have been also investigated.     

Effects of amines on the polymerization of isoprene with sec-butyllithium catalyst

Polymerization of isoprene (IP) with alkyllithium (RLi) catalysts in the presence of amines such as triethylamine (TEA), 1,2-dipiperidinoethane (DPPE) and N,N,N′,N′-tetramethyldiaminoalkanes [(CH₃)₂N(CH₂)_nN(CH₃)₂ where n=1, 2, 3, 4 and 6 (TMDAA)] has been studied. By adding the amines, the polymerization rate of IP was accelerated, and the contents of 3,4- and 1,2-units in the resulting polymers increased. The effects of methylene chain length of the TMDAA on the polymerization were examined. It was found that both the polymerization rates and the microstructure of the polymers depend on the methylene length of the TMDAA. The amines having 2 and 3 methylenes in (CH₃)₂N(CH₂)_nN(CH₃)₂ favoured production of the polymer consisting of predominantly 1,2- and 3,4-units. It was proposed that two types of active sites for the polymerization of IP were produced depending on the number n of the TMDAA. Two types of active species were confirmed to be produced with sec-BuLi in the presence of N,N,N′,N′-tetramethylethylenediamine (TMEDA) depending on the TMEDA/sec-BuLi mole ratios. © 1998 SCI.     

Hydrothermal Synthesis and Characterization of Trimethyltin(IV) Derivatives with 2-Carboxyethylphosphonic and Benzylphosphonic acid: X-ray Crystal Structures of 2D Network Polymers

Two organotin(IV) derivatives, {[(CH₃)₃Sn]₆·[O₃P(CH₂)₂CO₂]₂·3H₂O} _n 1 and {[(CH₃)₂Sn]₄·[O₃PCH₂Ph]₄} _n 2, were synthesized by the reaction of trimethyltin(IV) chloride, 2-carboxyethylphosphonic acid and benzylphosphonic acid, respectively. Characterization of complexes 1 and 2 were achieved using elemental analysis, IR, TGA, NMR (¹H, ¹³C, ³¹P and ¹¹⁹Sn) spectroscopy and X-ray crystallography diffraction analysis. X-ray characterization show that complexes 1 and 2 are 2D network structures.     

Polymerization of α-olefins and Hydrogenolysis of the Resulting Polyolefins with Hafnium Hydrides Supported on Silica

The reaction of Hf(CH₂ tBu)₄ with a silica surface treated at 800 °C affords the unique single site (≡SiO)Hf(CH₂ tBu)_3, 1, ((≡SiO) = silica surface ligand). Reaction of 1, with dihydrogen at temperatures (θ) ranging from 100 °C to 250 °C leads to different surface hydrides. At θ ≤ 100 °C, there is formation of [(≡SiO)Hf(CH₂ tBu)(H)₂], 2. For 100 ≤ θ ≤ 200 °C, 2 affords, [(≡SiO)₂Hf(H)₂], 3, and [(≡SiO)₃SiH]. For 150 ≤ θ ≤ 250 °C, 3, is totally converted into [(≡SiO)₃Hf(H)], 4, and [(≡SiO)₂Si(H)₂]. These different surface hafnium hydrides 2–4, which are obtained simultaneously but in various proportions were referred to as [Hf]_θ–H, (θ = 75, 100, 125, 150 and 250 °C). [Hf]₁₅₀–H is the most active catalyst in α olefin (ethylene, propene, isobutylene) polymerization at 25 °C and in polyolefin depolymerization at 150 °C under H₂ atmosphere. Although, there is a clear correlation between the catalytic activity both in polymerization and in depolymerization, and the amount of 3 and 4, it is not possible to establish which between the mono and the bis-hydride is the most active.     

Poly(methylphenylphosphazene)–Graft–Poly(methyl Methacrylate) Copolymers Via Atom Transfer Radical Polymerization

Atom transfer radical polymerization (ATRP) was used to graft poly(methyl methacrylate), PMMA, onto poly(methylphenylphosphazene), [(Me)(Ph)PN] _n , PMPP. A two-step process was used to convert a portion of the methyl substituents on [(Me)(Ph)PN] _n to –CH₂C(CH₃)₂OH groups and then to bromoalkyl groups, –CH₂C(CH₃)₂OC(=O)C(CH₃)₂Br, the latter of which served as initiation sites for ATRP of methyl methacrylate (MMA) in the presence of CuCl/bipyridine. Variations in the length of the grafted chains were investigated and the graft copolymers were compared to the parent polymer and blends of similar composition. The new bromoalkyl derivatives of [(Me)(Ph)PN] _n and the PMPP–graft–PMMA copolymers were characterized by elemental analysis, ¹H and ³¹P NMR spectroscopy, size exclusion chromatography (SEC), and differential scanning calorimetry (DSC). We dedicate this paper to Professor Harry R. Allcock for consistently maintaining the highest standards in his creative, pioneering work in inorganic rings and polymers.     

Polyhydrides of Sc,Zr and Hf and Their Proposed Formation.

Hydrogenation at 500 psi of (PNP)Sc(CH₃)₂ results in formation of a trinuclear polyhydride complex [(PNP)Sc]₃(μ₂-H)₄(μ₃-H)₂ ( 1 ) in 55 % yield. The solid-state structure shows a non-symmetric trinuclear species resulting from one pincer phosphine arm being demetallated, and where two hydrides bridge all three Sc centers, whereas the other four bridge two. Hydrogenation of (PNP)Zr(CH₃)₃ at 200 psi results instead in formation of a dinclear polyhydride species [(PNP)Zr(H)]₂(μ₂-H)₄ ( 2 ). Conducting the hydrogenation at atmospheric pressure, resulted instead in formation of the bridging methylidene complex [(PNP)Zr(CH₃)]₂(μ₂-H)₂(μ₂-CH₂) ( 3 ), which cleanly converted to 2 , upon hydrogenation at higher pressure. Both 2 and 3 were also structurally characterized. Hydrogenation of (PNP)Hf(CH₃)₃ at 200 psi resulted in incomplete hydrogenation with some formation of dinuclear mono- and dimethyl-polyhydride complexes [(PNP)Hf(CH₃)]₂(μ₂-H)₄ ( 4 ) and [(PNP)Hf(CH₃)][(PNP)Hf(H)](μ₂-H)₄ ( 5 ), which were identified by solid-state X-ray structural studies. Based on these results, we propose a pathway for the complete hydrogenation of (PNP)Zr(CH₃)₃ to 2 .     

Concave reagents 29 [1] Dendrimer fixed concave pyridine

A concave pyridine 1c has been attached to dendrimers of the Fréchet type by an ethylenoxide linker on the convex outside of the catalyst. Two generations of dendrons [G-1]-OH , [G-2]-OH , [G-1]-Br and [G-2]-Br and of dendrimers with 4,4′-dihydroxybiphenyl ( 3 ) and 1,1,1-tris(4-hydroxyphenyl)ethane ( 4 ) as di- and trivalent cores [G-1] ₂ –[C2] , [G-1] ₃ –[C3] and [G-2] ₃ –[C3] have been synthesized. The resulting molecules possess up to twelve concave catalytic pyridine centers on the outside of the molecules, and can be used as selective catalysts in the base catalyzed addition of alcohols to diphenylketene.     

Bis(cyclopentadienyl) lanthanide benzylthiolate: synthesis,molecular structure and catalytic property for ε-caprolactone –polymerization

Reaction of LnCl₃ first with three equivalent of C₅H₅Na in THF, then with one equivalent of benzyl mercaptan, led to complexes of [(C₅H₅)₂Ln(SCH₂Ph)]₂ (Ln?=?Sm(1), Yb(2)), being characterized by infrared spectra, elemental analyses and X-ray crystallography for 2. Complex 2 is a dimer with two thiolate ligands as bridging groups in eight coordinate. The Yb-S(benzyl) bonds in 2 (2.703(19) and 2.719(2) Å, respectively) were longer than the Yb-S(aryl) bonds (about 2.640 Å) in analogous complexes. The catalytic property for the polymerization of ε-caprolactone by 1 and 2 was studied. Similar experiment was also made with [(C₅H₅)₂Ln(SPh-p-CH₃)(THF)]₂ (Ln?=?Sm(3), Yb(4)) for comparison. It was found that complex 2 showed the activity best, and the activity decreased in the order of 2?>?3?>?1?>?4. When [ε-CL]₀/[Ln] was 500 and the polymerization temperature was 35°C, complex 2 catalyzed the polymerization in living character, which could not be achieved by lanthanide arylthiolates such as 3 and 4.     

Dendrimeric silanes for formation of metallosilicates: new heterogeneous catalysts for the epoxidation of alkenes with tert-butylhydroperoxide

New metallosilicate catalysts were prepared by reacting a silanol capped dendrimer, Si[CH₂CH₂Si(CH₃)₂OH]₄ with MCp₂Cl₂ (M = Ti^IV, Mo^VI, W^VI and V^V). The resulting Si[CH₂CH₂>Si(CH₃)₂OMCp₂Cl]₄compounds were incorporated in a silica matrix by the sol–gel method. The catalytic activity of the metallosilicates after calcination revealed excellent activity and selectivity towards epoxidation of alkenes with tert-butylhydroperoxide. Maximum activity was observed with molybdenum-containing materials. Analysis of the catalytic activity revealed that the catalysts were truly heterogeneous.     

Synthesis and properties of poly(phenylacetylene)s with pendant imino groups

Summary Polymerization of phenylacetylenes containing imino groups with a variety of transition metal catalysts was investigated. The monomers employed were N-(4-ethynylbenzylidene)aniline (1), N-(3-ethynylbenzylidene)aniline (2), N-(4-ethynylbenzylidene)-2,6-diisopropylaniline (3), N-(4-ethynylbenzylidene)-4-hexylaniline (4), N-(4-ethynylbenzylidene)butylamine (5), and N-(4-ethynylbenzylidene)octylamine (6). All of the monomers smoothly polymerized with [(nbd)RhCl]₂-Et₃N to give polymers in excellent yields, whereas no polymerization took place with W, Mo, and Fe catalysts. The produced polymers were orange to red solids and soluble in common organic solvents except for poly(1). UV-vis spectra of the polymers indicated that the main chains possess a similar degree of conjugation to that of poly(phenylacetylene). However, the stability of polymer backbone toward oxidative cleavage in solution remarkably improved, which is contributed by the electron-withdrawing character of imino groups. Received: 24 August 1999/Accepted: 29 September 1999     

Synthesis, Spectroscopic Characterization and Structures of Tributyltin(IV) 4-[((E)-1-{2-hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]benzoates. Toxicity Studies on the Second Larval Instar of the Anopheles stephensi Mosquito Larvae

A series of tributyltin(IV) complexes of 4-[((E)-1-{2-hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]benzoates have been investigated by ¹H, ¹³C, ¹¹⁹Sn NMR, IR and ¹¹⁹Sn M?ssbauer spectroscopic techniques in combination with elemental analyses. Single crystal X-ray crystallography of Bu₃Sn[O₂CC₆H₄{N=C(H)C₆H₃-2-OH(N=NC₆H₄CH₃-4)}-p] reveals a distorted tetrahedral structure which is further supported by ¹¹⁹Sn M?ssbauer data. Toxicity studies of the tributyltin(IV) complexes along with their ligands 4-[((E)-1-{2-hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]benzoic acids on the second larval instar of the Anopheles stephensi mosquito larvae are also reported.     

Hydrogenation of nitriles with iridium-triphenylphosphine complexes

Reactions of cationic iridium(I)-COD (COD = 1,5-cyclooctadiene) complexes, [Ir(COD)(PhCN)(PPh₃)]ClO₄ (1), [Ir(COD)(PPh₃)₂]ClO₄ (2) and [Ir(COD)(PhCN)₂]ClO₄ (3) with nitriles under H₂ catalytically produce primary, secondary and tertiary amines. Hydrogenation of nitriles (RCN) gives HCl salts of amines (RCH₂NH₂HCl, (RCH₂)₂NH HCl) in CH₂Cl₂. Secondary and tertiary amines seem to be produced by the reactions of RCN with primary and secondary amines, respectively under H₂ in the presence of catalysts. The hydrogenation in the presence of1 and2 is homogeneously catalyzed by soluble iridium-PPh₃ complexes formed in the reactions of1 and2 with H₂ and RCN whereas the hydrogenation in the presence of3 is heterogeneous by metallic iridium powders produced in the reduction of3 by H₂.     

Convenient Modular Syntheses of Fluorous Secondary Phosphines and Selected Derivatives

Reactions of the fluorous primary phosphines R_fn(CH₂)₂PH₂ [R_fn=(CF₂)_n−1CF₃; n=6, 8, 10] and R_fn′CHCH₂ [(n′=6, 8, 10) (1 : 1; THF, reflux) in the presence of AIBN give the title compounds [R_fn(CH₂)₂][R_fn′(CH₂)₂]PH [n/n′=6/6 ( 4 , 55%), 8/8 ( 5 , 58%), 10/10 ( 6 , 53%), 8/6 ( 7 , 52%), 10/8 ( 8 , 51%)] as low-melting white solids on up to 10-g scales. The chiral tertiary phosphine [R_f6(CH₂)₂][R_f8(CH₂)₂][R_f10(CH₂)₂]P ( 9 ) is similarly prepared from 7 and R_f10CHCH₂ in the presence of VAZO (neat, 100 °C; 67%). The reaction of 5 and THF⋅BH₃ yields the phosphine borane 5 ⋅BH₃ (95%). Additions of triphosgene [(CCl₃O)₂CO] to 5 or R_f8(CH₂)₂PH₂ give [R_f8(CH₂)₂]₂PCl or R_f8(CH₂)₂PCl₂, which are characterized in situ. The CF₃C₆F₁₁/toluene partition coefficients of 4 – 9 increase with the number and lengths of the R_fn segments.     

hERG Optimization of Benzofuro−Pyridine and Pyrazino−Indole Derivatives as MCHR1 Antagonists

Obesity is a global epidemic associated with multiple severe diseases. Several pharmacotherapies have been investigated including the antagonists of melanin concentrating hormone receptor 1 (MCHR1). The design, synthesis, and biological studies of novel MCHR1 antagonists based on benzofuro−pyridine and pyrazino−indole scaffold was performed. We confirmed that fine-tuning lipophilicity and basic pK_a by modifying the benzyl group and introducing different substituents on the aliphatic nitrogen sidechain decreases both hERG inhibition and metabolic clearance. We have succeeded to develop excellent in vitro parameters in the case of compounds 17 (4-[(5-chloropyridin-2-yl)methoxy]-1-[4-(2-hydroxyethyl)-8-oxa-4-azatricyclo[7.4.0.0²,⁷]trideca-1(13),2(7),9,11-tetraen-11-yl]-1,2-dihydropyridin-2-one monohydrochloride) and 23 g (4-[(5-chloropyridin-2-yl)methoxy]-1-(1,2,3,4-tetrahydropyrazino[1,2-a]indol-8-yl)pyridin-2(1H)-one monohydrochloride), which can be considered as valuable tools for further pharmacological investigation.     

A glutamic acid-based polymer keeping intact the integrity of all the three original functionalities of the amino acid

Dimethyl glutamate, on treatment with allyl bromide, afforded dimethyl N,N-diallylglutamate which upon alkaline ester hydrolysis followed by acidification with aqueous HCl gave N,N-diallylglutamic acid hydrochloride [(CH₂=CH–CH₂)₂NH⁺CH(CO₂H)(CH₂)₂CO₂H Cl^?] I. Using Butler’s cyclopolymerization protocol, new monomer I underwent ammonium persulfate-initiated polymerization to give pyrrolidine ring-embedded linear cyclopolymer II i.e. ?[?CH₂(C₄H₆)NH⁺{CH(CO₂H)(CH₂)₂CO₂H Cl^?}CH₂?]?_n retaining the integrity of all the three functionalities of glutamic acid. Under the influence of pH, the repeating units of triprotic acid (+) in II were equilibrated to those of water-insoluble diprotic polyzwitterionic acid (±) III, water-soluble monoprotic poly(zwitterion-anion) (±?) IV, and its conjugate base polydianion (=) V. The critical salt concentration required to promote water solubility of (±) III has been determined to be 0.548 M NaCl, 0.271 M NaBr, 0.133 M NaI. The basicity constants of the carboxyl groups and trivalent nitrogen in (=) V have been determined. A 5 ppm and 20 ppm concentrations of III are effective in inhibiting the precipitation of CaSO₄ from its supersaturated solution with a ≈100% scale inhibition efficiency at 40 °C for a duration of over 3 and 16 h, respectively.     

Polymerization of Cyclophosphazenes with Spriocyclic Methacrylate Containing Substituents

The radical addition polymerization and copolymerization of the cyclophosphazene monomers with spirocyclic methacrylate containing substituents, spiro(2,3-dioxypropylmethacryloyl)tetrachlorocyclotriphosphazene, N₃P₃Cl₄[OCH₂CH(OC(O)=CH₂)O] (1) and spiro((2-methyl-3-oxy-2-(oxymethyl)propyl)methacryloyl)tetrachlorocyclotriphosphazene, N₃P₃Cl₄[OCH₂CMe(CH₂OC(O)=CH₂)CH₂O] (2), has been investigated. In the case of 1, homopolymerization using AIBN as the initiator yielded only cross-linked solids. Copolymerization of 1 with methyl methacrylate was accomplished using VAZO 52 under milder initiation temperature. GPC of copolymer suggested a significant amount of chain transfer. Homopolymerization of 2 gave low isolated yields of the homopolymer but copolymerization with methyl methacrylate yielded the expected copolymers. The reactive chlorine atoms in the copolymers of 2 can be replaced by trifluoroethoxide or methyl amine. Thermal properties of the copolymers were examined by DSC, TGA and pyrolysis mass spectrometry.     

Synthesis, Characterization and Photoluminescence of Dimeric and Polymeric Metallaynes of Group 10–12 Metals Containing Conjugation-breaking Diphenylmethane Unit

A novel approach based on conjugation interruption was developed for a luminescent and thermally stable platinum(II) polyyne polymer trans-[–Pt(PBu₃)₂C≡C(C₆H₄)CH₂(C₆H₄)C≡C–] _n (1) containing the diphenylmethane chromophoric spacer. Particular attention was focused on the photophysical properties of this group 10 polymetallayne and comparison was made to its binuclear model complex trans-[Pt(Ph)(PEt₃)₂C≡C(C₆H₄)CH₂(C₆H₄)C≡CPt(Ph)(PEt₃)₂] (2) and their closest group 11 gold(I) and group 12 mercury(II) neighbors, [MC≡C(C₆H₄)CH₂(C₆H₄)C≡CM] (M = Au(PPh₃) (3), HgMe (4)). The regiochemical structures of these angular-shaped compounds were studied by various spectroscopic analyses. Upon photoexcitation, each of them emits an intense purple-blue fluorescence emission in the near UV region in dilute fluid solutions at room temperature. Harvesting of organic triplet emissions harnessed through the strong heavy-atom effects of group 10–12 transition metals was examined. These metal-containing phenyleneethynylenes spaced by the conjugation-breaking CH₂ unit were found to have high optical gaps and high-energy triplet states. The influence of metal and sp³-hybridized methylene conjugation-interrupters on the intersystem crossing rate and the spatial extent of the lowest singlet and triplet excitons was fully elucidated. Our investigations indicate that high-energy triplet states in these materials intrinsically give rise to very efficient phosphorescence with fast radiative decays. Dedicated to Professor Didier Astruc in recognition of his outstanding contribution to metallodendrimers and polymers.