Poly(Urethane–Urea) Varnishes Containing Tributyltin Groups

New poly(urethane–urea) varnishes containing tributyltin groups were prepared by the reaction of dibenzyldiisocyanate in excess with a macrodiol (PEGA-2000), trimethylolpropane, diethylene glycol and a bisalcohol maleimide monomer containing tributyltin carboxylate group. Tributyltin maleimide monomers were obtained from 4-{3,4-bis[(2-hydroxyethyl)sulfanyl]-2,5-dioxo-2,5-dihydro-1H-pyrrol-1-yl}benzoic acid and bis(tributyltin) oxide. Structure of monomers and polymers was confirmed by the IR, NMR spectroscopy and elemental analysis. The polymer films were characterized by dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), X-ray diffractions, thermogravimetric (TGA) and stress–strain measurements.     

Synthesis and Characterization of Some Triphenyltin(IV) Complexes from Sterically Crowded [((E)-1-{2-Hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]acetate Ligands and Crystal Structure Analysis of a Tetrameric Triphenyltin(IV) Compound

Four new triphenyltin(IV) complexes containing [((E)-1-{2-hydroxy-5-[(E)-2-(aryl)-1-diazenyl]phenyl}methylidene)amino]acetate ligands (L) have been synthesized with formulations of Ph₃SnLH. They have been studied by multinuclear (¹H, ¹³C, ¹¹⁹Sn) NMR, ¹¹⁹Sn M?ssbauer and IR spectroscopy. A full characterization of one complex, Ph₃SnL¹H (1), was accomplished by single crystal X-ray crystallography, which revealed the compound to be a macrocyclic tetramer. In the tetramer, the five coordinate tin atoms have distorted trigonal bipyramidal geometries with the three phenyl groups occupying equatorial positions, while an oxygen atom of the carboxylate group of one L ligand and the oxide O-atom (formerly the hydroxy group) of a second L ligand in an apical positions. The carboxylate ligands bridge adjacent tin atoms and coordinate in the zwitterionic form with the phenolic proton moved to the nearby nitrogen atom. ¹¹⁹Sn NMR results indicate that the tetrameric structures of the complexes in the solid state, in which the tin atoms are five-coordinated, dissociate in solution to yield four coordinate monomeric species.     

Triphenyltin (IV) derivatives of N-acetyl amino acids,N-acetyl dipeptides and tripeptides: Preparation,NMR investigations and NMR spectroscopic resolution of the enantiomeric composition

Triphenyltin(IV) derivatives of N-acetyl amino acids ( 1a–g ) and N-acetyl di- ( 2a–f ) or tripeptides ( 3 ) mostly in the (L )- and the racemic (DL )-form have been prepared from bis(triphenyltin)oxide and the appropriate N-acetyl amino acid or N-acetyl peptide using various dehydrating agents. The compounds were characterized by NMR spectroscopy and elemental analysis. These compounds were studied at different concentrations and temperatures, revealing a strong self-association tendency. NMR investigations were undertaken in order to highlight preferred conformations of the peptide derivatives due to possible strong intramolecular associations between tin and nucleophilic donor atoms of the peptide moiety in weakly polar solvents. No preferred conformation was found which was in accordance with the underivatized peptides. The enantiomeric composition was determined by means of ¹H NMR spectroscopy using (−)-quinine hydrochloride and S-(−)-1-phenylethylamine as chiral solvating agents.     

Preparation of Ir0.3Sn(0.7-x)Ti x O2 Electrodes by the Polymeric Precursor Method: Characterization and Lifetime Study

Thin film electrodes of nominal composition Ir_0.3Sn_(0.7-x)Ti _x O₂ (0 ≤ x ≤ 0.7) were prepared by decomposition of polymeric precursors. The solutions used to prepare the electrodes were obtained by mixing of the precursor salts with a mixture of ethylene glicol and citric acid. The films were burned at 400 °C and characterized by X-ray diffraction, scanning electronic microscopy, energy dispersive X-ray spectroscopy and cyclic voltammetry. The electrodes were submitted to high anodic current density in order to evaluate their lifetime in perchloric acid solution. Results show that the electrodes present compositions similar to that of the precursor solutions, suggesting that there is no loss of tin during the calcination step. The electrodes had large surface area and higher lifetime in comparison with electrodes of similar composition prepared by other methods. The possible mechanisms involved in deactivation of the electrodes are discussed.     

Organotin polymers. IV. Binary and ternary copolymerizations of tributyltin acrylate and methacrylate with styrene,allyl methacrylate,butyl methacrylate,butyl acrylate,and acrylonitrile

The monomer reactivity ratios for the copolymerization of tributyltin acrylate with styrene and allyl methacrylate have been found to be r₁ = 0.213, r₂ = 1.910 and r₁ = 0.195, r₂ = 2.257, respectively. Also, the copolymerization parameters of tributyltin methacrylate with styrene and allyl methacrylate were as follows: r₁ = 0.256, r₂ = 1.104 and r₁ = 2.306, r₂ = 1.013. Copolymerization reactions were carried out in solution at 70°C using 1 mole % AIBN, and the copolymer compositions were determined by tin analysis. Ternary copolymerization of the three systems butyl methacrylate–tributyltin methacrylate–acrylonitrile, butyl acrylate–tributyltin methacrylate–acrylonitrile, and styrene–tributyltin acrylate–acrylonitrile have been studied, and the terpolymer composition of each system was determined through tin and nitrogen analyses. The variation of instantaneous and average terpolymer composition with conversion fit satisfactorily the experimental results over a wide range of conversion.     

有机锡杀菌剂的研究Ⅱ——三丁基锡硫醚的合成

本文叙述8种三丁基锡硫醚的合成,这些新化合物是用相应的三丁基氧化锡与硫醇脱水制得,并测定了各化合物的一些物理常数。 初步药效测定结果说明,OT029对于水稻纹枯病具有显著杀菌作用,且药害较低。     

Grafting. IV. Graft tercopolymers as antifouling resin

A graft tercopolymer CLR-g-(MMA–TBTMA) based on chlorinated rubber as the backbone and binary copolymer of methyl methacrylate and tributyltin methacrylate as grafted chains has been synthesized. This graft copolymer has been used for the formulation of controlled-release antifouling paints, and leaching rate behavior of toxin from such paints has been studied. The data have been compared with those obtained using controlled-release antifouling paint based on linear chain copolymer of methyl methacrylate and tributyltin methacrylate. The paint based on grafted copolymer is characterized by having a lower leaching rate and reduced time for attainment of steady-state leaching. Raft exposure studies indicate longer antifouling life compared to that of linear chain copolymer-based paint both having the same dry paint film thickness.     

Synthesis of Triorganostannate Esters of Dicarboxylic Acids: X-ray Crystal Structure of Polymeric Triethylammonium 2,5-Thiophenedicarboxylatotriphenylstannate

The triethylammonium 2,5-thiophenedicarboxylatotriorganostannates, [(C₂H₅)₃ NH]-[R₃Sn((O₂C)₂C₄H₂S)] (R = Me (1), n-Bu (2), Ph (3), PhCH₂ (4)), have been prepared from triethylamine, 2,5-thiophenedicarboxylic acid and triorganotin chloride. All the compounds, 1–4, have been characterized by elemental, IR and ¹H-NMR analyses. An X-ray analysis of the R = phenyl compound shows that the structure is polymeric with neighboring triorganotin centers being linked by dicarboxylate ligands. Each carboxylate moiety is involved in coordination to a Sn atom via one O atom only showing that the Sn atoms are five-coordinate and exist in trigonal bipyramidal geometries. Moreover, the ammonium nitrogen is hydrogen bonded to the carbonyl oxygen.     

Tin(IV) Polymers: Part 1. Synthesis of Diorganotin Esters of Thiosalicylic Acid: X-ray Crystal Structure of Polymeric Thiosalicylatodiorganotin

Thiosalicylatodiorganotin, [R₂Sn(O₂CC₆H₄S)]_n, (R=Me (1), n-Bu (2), Ph (3), 3-Cl–PhCH₂ (4)), are prepared from thiosalicylic acid and diorganotin chlorides. All the compounds, 1–4, are characterized by elemental analysis as well as IR and ¹H-NMR spectroscopy. X-ray crystallographic analysis of the 2 and 4 shows that the structures are polymeric with neighboring diorganotin centers being linked by one O-atom of the carboxylate ligands. The carboxylate moiety is involved in coordination to one Sn atom via one O-atom while the other O-atom coordinates to the neighboring Sn atom. The mercaptotropone sulfur atom is bonded to the central Sn atom thereby establishing that Sn is five-coordinate and exists in a trigonal bipyramidal geometry.     

Oxidation in fish lipids during thermal stress as studied by 13C nuclear magnetic resonance spectroscopy

¹³C Nuclear magnetic resonance spectroscopy has been applied to elucidate the mechanism of lipid oxidation occurring during thermal treatment of fish. Effects of temperature and time of processing have been studied by means of a model system of lipids, extracted from salmon (Salmo salar) muscle, to simulate industrial conditions of canning. Unsaturated fatty acids located at the sn-2 position of the glycerol moiety were the most prone to oxidative damage. Regarding the mechanism of the reaction, results inferred from olefinic and methylenic resonances indicated a higher susceptibility of the allylic sites closest to the carbonyl group, followed by those placed near the methyl terminal group. Unsaturations located in the middle of the carbon chain did not show much damage. The glyceryl region provided an unusual resonance at 53.4 ppm, which could be assigned to a hydroxylic compound formed during process.     

Remarkable asymmetric induction from remote stereocenters in conjugate addition chemistry for the synthesis of alkyl-branched α, ω-diaminoazelates

Conjugate addition of aryl Grignard reagents to (2S, 5E, 8S)-di-tert-butyl 4-oxo-2,8-bis-[N-(PhF)amino]non-5-enedioate ( 6 , PhF = 9-(9-phenyl-fluorenyl)) in THF proceeded with complete chemoselectivity and >9:1 stereoselectivity to provide predominantly (2S,6S,8S)-6-aryl 4-oxo-2,8-diamino-azelates 7 . In the presence of magnesium dibromide, diastereoselectivity in the addition of PhMgBr to enone 6 was improved to 15:1 in favor of the 6S-isomer. Although lower chemoselectivity and stereoselectivity were obtained from the analogous reaction of 6 with isopropyl magnesium bromide in the absence of MgBr₂, both were improved significantly when the addition reaction was performed in the presence of MgBr₂. In contrast, the corresponding higher-order cyanocuprates reacted with low diastereoselectivity on 6 by a 1,4-addition pathway. In an attempt to identify the source of the high selectivity in the conjugate addition chemistry with 6 and Grignard reagents, the syntheses of enones 12 and 13 provided model systems in which one of the two amino carboxylate moieties of 6 was replaced by a branched alkyl substituent. Conjugate addition reactions on 12 and 13 demonstrated that chemoselectivity with Grignard reagents in the 1,4-addition reaction was contingent on the presence of an amino carboxylate moiety near the ketone of the enone system. Furthermore, because diastereoselectivity with Grignard reagents was significantly lower in additions to amino enones 12 and 13 relative to diamino enone 6 , the presence of both amino carboxylate moieties has been highlighted as an important factor for remarkable asymmetric induction in the conjugate addition of Grignard reagents.     

Palladium Nanoparticles in Suzuki Cross‐Couplings: Tapping into the Potential of Tris‐Imidazolium Salts for Nanoparticle Stabilization

Inspired by the proclivity of various palladium sources to form nanoparticles in imidazolium‐based ionic liquids, we now report that tris‐imidazolium salts bearing hexadecyl chains and a bridging mesitylene moiety are potent stabilizers of palladium nanoparticles efficiently prepared via a Chaudret‐type hydrogenation of the bis(dibenzylideneacetone)palladium(0). The palladium nanoparticles have been isolated in pure form and characterized by ¹H nuclear magnetic resonance, transmission electron microscopy, electron diffraction and dynamic light scattering. The new materials proved effective in Suzuki cross‐coupling at a loading of 0.2% palladium. Thus, using a tris‐imidazolium iodide‐palladium material, a series of biaryl products has been prepared starting from aryl bromides and some activated chlorides. The possibility that this catalytic activity might be due to the formation of palladium N‐heterocyclic carbenes has been addressed through solid state ¹³C NMR and the synthesis of an imidazolium analogue in which the acidic 2‐H was replaced with a methyl group.     

Synthesis and characterization of new water‐soluble metal–polymer complex and its application for arsenite retention

New water‐soluble metal–polymers of poly(acrylic acid)s (AA) with different amounts of tin (3, 5, 10, and 20 wt %) were synthesized and characterized. The materials were characterized by ¹H NMR and FTIR spectroscopy, X‐ray diffraction (XRD), specific area by isotherm of CO₂, and thermogravimetry‐differential scanning calorimetry (TG‐DSC). The synthesized material is crystalline and shows an average crystal size 90–130 nm and has a high thermal stability (>200°C). Texturally, they are complexes of small specific area, which decreases when the crystal size increases with the tin content. Presumably, the Sn(II) ions coordinate through 2‐4 carboxylate groups by a conventionally bidentate structure; however, they are not symmetric. Studies have been dedicated to support of tin in polymers to increase its efficiency in eliminating pollutants. The tin‐metal salt is added to the poly(AA) matrix to increase its ability to remove As(III) from an aqueous solution. The liquid‐phase polymer‐based retention technique is applied to retain and separate contaminants from water. The analysis of As(III) and As(V) species was made by combining liquid high‐resolution chromatographic coupled to hydride generation absorption atomic spectrophotometer (HPLC‐HG‐AAS). All indicated that As(III) was the predominant species bound to the polymer complex for the pH range 4–8. The polymers containing 10 and 20 wt % Sn presented the highest retention of 70 and 90% As(III), respectively. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Enhancement of the electrooxidation of ethanol on a Pt–PEM electrode modified by tin. Part I: Half cell study

The direct platinisation of a solid polymer electrolyte (Nafion^® membrane) was realized by chemical reduction of a platinum salt. The Pt–PEM electrodes thus obtained were modified by tin to improve the electrocatalytic activity towards the electrooxidation of ethanol. The Pt–PEM and Pt–Sn–PEM electrodes were characterized by TEM, EDX and XRD analysis, cyclic voltammetry, and their polarisation curves for the electrooxidation of ethanol were determined under quasisteady state conditions.     

Preparation and properties of new surfactants containingd-glucosamine as the building block

Three types of new surfactants were prepared by usingN-acetyl-d-glucosamine as a starting material. The first type of surfactant, sodium methyl 4,6-O-alkylidene-2-(carboxyl-atomethylamino)-2-deoxy-d-glucopyranoside, was prepared successively by the following treatments: methyl glucosidation ofN-acetyl-d-glucosamine, transacetalization with an appropriate aldehyde dimethyl acetal, deacetylation, and finally reaction of the resulting methyl-4,6-O-alkylidene-2-amino-2-deoxy-d-glucopyranoside (2-amino precursor) with bromoacetic acid. The reaction of this 2-amino precursor with methyl iodide yielded the second type of surfactant, methyl 4,6-O-alkylidene-2-deoxy-2-(trimethylammonio)-d-glucopyranoside iodide, in excellent yield. The last type of compound, sodium methyl 2-acetamide-4,6-O-alkylidene-3-O-[1-(carboxylato)-ethyl]-2-deoxy-d-glucopyranoside, was synthesized by the reaction of methyl 2-acetamide-4,6-O-alkylidene-2-deoxy-d-glucopyranoside with 2-chloropropionic acid. Concerning the two carboxylate types of surfactants, the compounds containing a C₉ or C₁₁ hydrophobic chain in the alkylidene part showed higher water solubility than the corresponding compounds containing a C₇ hydrophobic chain. Both the micelle-forming property and the ability to lower the surface tension of these carboxylate types of compounds increased with an increase in the length of the hydrophobic chain in the alkylidene part. These compounds can be applied to new acid-decomposable types of cleavable surfactants because they contain an acetal group. The acetal bond of the ammonium type of compound was cleaved more slowly than that of the corresponding carboxylate types of surfactants in 2% aqueous HCI solution. The biodegradabilities of these compounds were also determined.     

Substrate Enolate Intermediate and Mimic Captured in the Active Site of Streptomyces coelicolor Methylmalonyl-CoA Epimerase**

Methylmalonyl-CoA epimerase (MMCE) is proposed to use general acid-base catalysis, but the proposed catalytic glutamic acids are highly asymmetrical in the active site unlike many other racemases. To gain insight into the puzzling relationships between catalytic mechanism, structure, and substrate preference, we solved Streptomyces coelicolor MMCE structures with substrate or 2-nitropropionyl-CoA, an intermediate/transition state analogue. Both ligand bound structures have a planar methylmalonate/2-nitropropionyl moiety indicating a deprotonated C2 with ≥4 Å distances to either catalytic acid. Both glutamates interact with the carboxylate/nitro group, either directly or through other residues. This suggests the proposed catalytic acids sequentially catalyze proton shifts between C2 and carboxylate of the substrate with an enolate intermediate. In addition, our structures provide a platform to design mutations for expanding substrate scope to support combinatorial biosynthesis.     

Synthesis, X-ray structure and Hg, Se CP MAS NMR studies on the first tris(imidazolidine-2-selone) mercury complex: {Chloro-tris[N-methyl-2(3H)-imidazolidine-2- selone]mercury(II)}chloride

A novel cationic Hg(II) complex has been synthesized with N-methyl-imidazolidine-2-selone ligand. The tris(N-Methyl-imidazolidine-2-selone) mercury(II) complex, [(MeImSe)₃HgCl]⁺Cl⁻ (1), has been characterized by single crystal X-ray analysis and CP MAS ¹⁹⁹Hg and ⁷⁷Se NMR.     

Thermal transitions of ethylene-vinyl chloride copolymers and their blends

Differential Scanning Calorimetry (DSC) measurements were performed on a series of ethylene-vinyl chloride copolymers (E-V) prepared via reductive dechlorination of poly(vinyl chloride) with tributyltin hydride. The copolymers were identical in chain length and branching distribution; differing only in comonomer content, sequence distribution, and stereoregularity of adjacent —V— units. Extrapolation of glass transition temperatures, T_g, measured for our E-V copolymers to pure polyethylene (PE) predicted a T_g = ?85 ± 10°C for amorphous PE. E-V copolymers with greater than 60 mol percent —E— units exhibited melting endotherms from 20 to 128°C and degrees of crystallinity from 12 to 63 percent. The melting point depressions observed for our E-V copolymers were in agreement with Flory's theory, if the ? CH₂? CH₂ moiety is considered to be the crystallizable unit and the moiety is assumed to prevent the ? CH₂? CH₂? units attached on either side from being incorporated into the crystal. In general, the E-V copolymer blends with PE were incompatible, while those with PVC were compatible only for E-V copolymers with high V contents (>80 mol percent). Blends of the amorphous E-V copolymers were found compatible if their V contents differed by less than 15 mol percent, while blends where one or both E-V copolymers are crystalline were found to be incompatible. The properties of these copolymers will be discussed in terms of their microstructure.     

Electrophilic Stannylation of Arenes: A New SEAr Reaction

Electrophilic “trifluoroacetatotin(IV)” has been prepared by reaction of tin oxide with trifluoroperacetic acid/trifluoroacetic anhydride, and by reaction of tetraphenyltin with excess trifluoroacetic acid. The electrophilic tin(IV) material prepared by either route reacts reversibly with arenes to make aryl‐tin compounds and trifluoroacetic acid. The compounds (C₆H₅)₂Sn₄O₂(CF₃COO)₁₀ and (xylyl)₂Sn₄O₂(CF₃COO)₁₀ have been obtained from the reactions with benzene and p‐xylene, respectively, and their molecular structures determined by X‐ray crystallography. Tin now joins Pb, Tl, and Hg in the list of main group metals whose trifluoroacetato complexes can metalate arenes by C−H activation.