Organolanthanides with 3-(2-pyridylmethyl) indenyl ligands: synthesis, crystal structures and catalytic activities of divalent complexes for epsilon-caprolactone polymerization

Reaction of 3-(2-pyridylmethyl)indenyl lithium (1) with LnI(2)(THF)(2) (Ln = Sm, Yb) in THF produced the divalent organolanthanides (C5H4NCH2C9H6)(2)Ln(II)(THF) (Ln = Sm (2), Yb (3)) in high yield. 1 reacts with LnCl(3) (Ln = Nd, Sm, Yb) in THF to give bis(3-(2-pyridylmethyl)indenyl) lanthanide chlorides (C5H4NCH2C9H6)(2)Ln(III)Cl (Ln = Nd (4), Sm (5)) and the unexpected divalent lanthanides 3 (Ln = Yb). Complexes 2-5 show more stable in air than the non-functionalized analogues. X-ray structural analyses of 2-4 were performed. 2 and 3 belong to the high symmetrical space group (Cmcm) with the same structures, they are THF-solvated 9-coordinate monomeric in the solid state, while 4 is an unsolvated 9-coordinate monomer with a trans arrangement of both the side-arms and indenyl rings in the solid state. Additionally, 2 and 3 show moderate polymerization activities for F-caprolactone (CL).

Syntheses and crystal structures of bis(tetrahydrofurfurylindenyl) lanthanocene chlorides (C4H7OCH2C9H6)(2)LnCl (Ln = La, Lu)

Reaction of two equivalents of tetrahydrofurfuryl indenyl lithium with anhydrous lanthanide trichlorides in THF afforded bis(tetrahydrofurfurylindenyl) lanthanide chlorides (C4H7OCH2C9H6)(2)LnCl, Ln=La(l), Pr(2), Lu(3). Complexes I and 3 are characterized by single-crystal analysis. The results of crystal structural determination reveal that they are 9-coordinate monomeric intramolecular complexes with a trans arrangement of both the sidearms and indenyl rings in the solid state. The effects of rare earth ionic radii on the structures Of (C4H7OCH2C9H6)(2)LnCl are discussed.

Syntheses and characterization of half-sandwich zirconium complexes with dichalcogenolate o-carborane ligands

Metallocene complex (Cp2ZrCl2)-Zr-tt (Cp-tt = eta(5)-1,3-(Bu2C5H3)-Bu-t) (1) has been prepared from the reaction of LiCptt with ZrCl4 in good yield. Reactions of 1 with dilithium dichalcogenolate o-carboranes afforded new type of half-sandwich compounds with dichalcogenolate o-carboranyl ligands [Li(THF)(4)][(CpZr)-Zr-tt(E2C2B10H10)(2)] (E = S, 2a; E = Se, 2b) in which only one cyclopentadienyl ring ligand existed. Complexes 1 and 2a were structurally characterized by X-ray analyses. In complex 2a, the Zr(IV) ion is eta(5)-bound to one 1,3-di-tert-cyclopentadienyl ring and a-bound to four mu(2)-sulfur atoms of two dithio-carboranes. The zirconium atom and four sulfur atoms form a distorted pyramid. The coordination sphere around the zirconium atom resembles in a piano stool structure with four legs of sulfur atoms and the fulcrum at the zirconium atom.

Synthesis and characterization of hyperbranched poly(ester-amide)s from commercially available dicarboxylic acids and multihydroxyl primary amines

A new method for syntheses of hyperbranched poly(ester-amide)s from commercially available A(2) and CBx type monomers has been developed on the basis of a series of model reactions. The aliphatic and semiaromatic hyperbranched poly(ester-amide)s with multihydroxyl end groups are prepared by in situ thermal polycondensation of intermediates obtained from dicarboxylic acids (A(2)) and multihydroxyl primary amines (CBx) in N,N-dimethylformamide. Analyses of FTIR, H-1 NMR, and C-13 NMR spectra revealed the structures of the polymers obtained. The MALDI-TOF MS of the polymers indicated that cyclization side reactions occurred during polymerization. The hyperbranched poly(ester-amide) s contain configurational isomers observed by C-13 and DEPT C-13 NMR spectroscopy. The DBs of the polymers were determined to be 0.38-0.62 by H-1 NMR or quantitive C-13 NMR and DEPT 135 spectra. These polymers exhibit moderate molecular weights, with broad distributions determined by size exclusion chromatography ( SEC), and possess excellent solubility in a variety of solvents such as N, N- dimethylacetamide, dimethyl sulfoxide, tetrahydrofuran, and ethanol, and display glass-transition temperatures (T(g)s) between -2.3 and 53.2 degrees C, determined by DSC measurements.

Synthesis and structural characterization of beta-diketiminate-lanthanide Amides and their catalytic activity for the polymerization of methyl methacrylate and epsilon-caprolactone

The synthesis and catalytic activity of lanthanide monoamido complexes supported by a beta-diketiminate ligand are described. Donor solvents, such as DME, can cleave the chloro bridges of the dinuclear beta-diketiminate ytterbium dichloride {[(DIPPh)(2)nacnac]YbCl(mu-Cl)(3)Yb[(DIPPh)(2)nacnac](THF)} (1) [(DIPPh)(2)nacnac = N,N-diisopropylphenyl-2,4-pentanediimine anion] to produce the monomeric complex [(DIPPh)(2)nacnac]YbCl2(DME) (2) in high isolated yield. Complex 2 is a useful precursor for the synthesis of beta-diketiminate-ytterbium monoamido derivatives. Reaction of complex 2 with 1 equiv of LiNPr2i in THF at room temperature, after crystallization in THF/toluene mixed solvent, gave the anionic beta-diketiminate-ytterbium amido complex [(DIPPh)(2)nacnac]Yb(NPr2i)(mu-Cl)(2)Li(THF)(2) (3), while similar reaction of complex 2 with LiNPh2 produced the neutral complex [(DIPPh)(2)nacnac]Yb(NPh2)Cl(THF) (4). Recrystallization of complex 3 from toluene solution at elevated temperature led to the neutral beta-diketiminate-lanthanide amido complex [{(DIPPh)(2)nacnac}Yb(NPr2i)(mu-Cl)](2) (5). The reaction medium has a significant effect on the outcome of the reaction.

Syntheses of chromium(III) complexes with Schiff-base ligands and their catalytic behaviors for ethylene polymerization

A series of chromium(III) complexes LCrCl3 (4a-c) bearing chelating 2,2'-iminodiphenyisulfide ligands [L = (2-ArMeC=NAr)(2)S] was synthesized in good yields from the corresponding ligands and CrCl3.(THF). Using modified methylaluminoxane (MMAO) as a cocatalyst, these complexes display moderate activities towards ethylene polymerization, and produce highly linear polyethylenes with broad molecular weight distribution. Polymer yields, catalyst activities and the molecular weights, as well as the molecular weight distributions of the polymers can be controlled over a wide range by the variation of the structures of the chromium(III) complexes and the polymerization parameters, such as Al/Cr molar ratio, reaction temperature and ethylene pressure.

Titanium complexes with novel triaryl-substituted phosphinimide ligands: Synthesis, structure and ethylene polymerization behavior

A series of titanium phosphinimide complexes [Ph2P(2-RO-C6H4)(2)TiCl2 (7, R = CH3; 8, R = CHMe2) and (PhP(2-Me2CHOC6H4)][THF]TiCl3 (9) have been prepared by reaction of TiCl4 with the corresponding phosphinimines under dehalosilylation. The structure of complex 9 has been determined by X-ray crystallography, and a solvent molecule THF was found to be coordinated with the central metal and the Ti-O bond was consistent with the normal Ti-O (donor) bond length. The complexes 7 and 8 displayed inactive to ethylene polymerization, and the complex 9 displayed moderate activity in the presence of modified methylaluminoxane (MMAO) or i-BU3Al/Ph3CB(C6F5)(4), and this should be partly attributed to coordination of THF with titanium and the steric effect of two iso-propoxyl. And catalytic activity up to 32.2 kg-PE/(mol-Ti h bar) was observed.

Solvent and polymer concentration effects on the surface morphology evolution of immiscible polystyrene/poly(methyl methacrylate) blends

The effects of solvent nature on the surface topographies of polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend films spin-coated onto the silicon wafer were investigated. Four different solvents, such as ethylbenzene, toluene, tetrahydrofuran and dichloromethane, were chosen. They are better solvents for PS than that for PMMA. When dichloromethane, tetrahydrofuran and toluene were used, PMMA-rich phase domains protruded from the background of PS. When ethylbenzene was used, PS-rich phase domains elevated on the average height of PMMA-rich phase domains. In addition, continuous pits, networks and isolated droplets consisted of PS formed on the blend film surfaces with the decrease of polymer concentrations. The mechanism of the surface morphology evolution was discussed in detail.

Synthesis, structure and ethylene polymerization of group 4 complexes with phosphinoamide ligands

Group 4 complexes containing diphosphinoamide ligands [Ph2PNR](2)MCl2 (3: R = Bu-t, M = Ti; 4: R = Bu-t, M = Zr; 5: R = Ph, M = Ti; 6: R = Ph, M = Zr) were prepared by the reaction Of MCl4 (M = Ti; Zr) with the corresponding lithium phosphinoamides in ether or THF. The structure of [(Ph2PNBu)-Bu-t](2)TiCl2 (3) was determined by X-ray crystallography. The phosphinoamides functioned as eta(2)-coordination ligands in the solid state and the Ti-N bond length suggests it is a simple single bond. In the presence of modified methylaluminoxane or i-Bu3Al/Ph3BC(C6F5)(4), catalytic activity of up to 59.5 kg PE/mol cat h bar was observed.

Preparation and characterization of post-derivatives from functional polystyrene (ATRP) with p-nitroaniline-azomethine phenol and their thermal and optical study

The functional polystyrene, (Cl-PS)(2)-CHCOOCH2CH2OH ( designated as XPSt and coded P2) was prepared by ATRP at 130(0)C using CuCl and bipyridine as catalysts, 2,2-dichloro acetate-ethylene glycol (DCAG) as multifunctional initiator and THF as solvent. 4-Nitoroaniline azomethine-4' phenol (P1) as chromophores were covalently linked to the functional end groups of the polymer by using simple displacement reaction. The functional polystyrenes, namely XPSt (P2) and (PS)(2)-CHCOOCH2CH2OH, designated as X-PSt and coded P3 and their post-derivatives, namely, DXPSt (P4) and DX-PSt (P5) respectively were characterized by IR, NMR and UV spectroscopies, gel permeation chromatography (GPC) and thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), polarising optical microscopy (POM) and XRD studies. DSC showed that incorporation of chromophores in the side chains of polymers towards the polystyrene moiety increases the rigidity of the polymer and subsequently, its glass transition temperature; however the incorporation of side chain towards the alcoholic functional group decreases the glass transition temperature. The post derivatives do not play any significant role to increase the thermal stability ( TGA).

合金化程度对炭载Pt-Ru催化剂性能的影响

在含四氢呋喃(THF)的水溶液中,室温下用NaBH4还原H2PtC l6和RuC l3制得Pt-Ru/C催化剂.其Pt-Ru粒子的合金化程度较高,平均粒径较小,相对结晶度较低.因此对甲醇氧化的电催化活性远高于Pt-Ru粒子的平均粒径和相对结晶度相似的,而且Pt-Ru合金化程度低的商业化的E-TEK的Pt-Ru/C催化剂,表明Pt-Ru的合金化程度对Pt-Ru/C催化甲醇氧化的电催化活性有很大的影响.

一种制备碳载高合金化Pt-Ru催化剂的方法

提出了在四氢呋喃(THF)和H2O混合溶液中用一般的化学还原法在室温下制备碳载Pt-Ru(Pt-Ru/C)催化剂的新方法。与在纯水中制得的Pt-Ru/C催化剂相比,其Pt-Ru粒子的合金化程度高、平均粒径较小且相对结晶度低,因此,该催化剂对甲醇氧化的电催化活性远高于在纯水中制得的Pt-Ru/C催化剂。高合金化程度的原因是H2PtCl6和RuCl3在THF和H2O混合溶液中的起始还原电位相近。此外,在THF和H2O混合溶液中,THF和H2O的体积比的改变并不影响制得的Pt-Ru/C催化剂中Pt-Ru粒子的合金化程度,但对Pt-Ru粒子的粒径以及相对结晶度有较大影响。

Synthesis and characterization of hyperbranched aromatic poly(ester-imide)s

The synthesis and characterization of hyperbranched aromatic poly(ester-imide)s are described. A variety of AB(2) monomers, N-[3- or 4-bis(4-acetoxyphenyl)toluoyl]-4-carboxyl-phthalimide and N-{3- or 4-[1,1-bis(4-acetooxyphenyl)]ethylphenyl}-4-carboxy phthalimides were prepared starting from condensation of nitrobenzaldehydes or nitroacetophenones with phenol and used for synthesis of hyperbranched poly(ester-imide)s containing terminal acetyl groups by transesterification reaction. These hyperbranched poly(ester-imide)s were produced with weight-average molecular weight of up to 6.87 g/mol. Analysis of H-1 NMR and C-13 NMR spectroscopy revealed the structure of the four hyperbranched poly(ester-imide)s. These hyperbranched poly(ester-imide)s exhibited excellent solubility in a variety of solvents such as N,N-dimethylacetamide, dimethyl sulfoxide, and tetrahydrofuran and showed glass-transition temperatures between 217 and 255 degreesC. The thermogravimetric analytic measurement revealed the decomposition temperature at 10% weight-loss temperature (T-d(10)) ranging from 365 to 416 degreesC in nitrogen.

AFM study of the self-assembly behavior of hexa-armed star polymers with a discotic triphenylene core

The size-armed polystyrenes and poly-(methyl methacrylate)s with a triphenylene core showed different self-assembling patterns, isolated cylinders for polySt on mico and highly ordered cylindrical pores for polyMMA on a silicon water. With a decrease of polymer concentration in tetrahydrofuran (HHF), the size and height of cylinders decreased for polySt, but fur polyMMA, the size and depth of the cylindrical pores increased. Slow evaporation of the solvent and a low molecular weight favored the formation of regular patterns.

Ring-opening polymerization and block copolymerization of L-lactide with divalent samarocene complex

Divalent samarocene complex [(C5H9C5H4)(2)Sm(tetrahydrofuran)(2)] was prepared and characterized and used to catalyze the ring-opening polymerization of L-lactide (L-LA) and copolymerization of L-LA with caprolactone (CL). Several factors affecting monomer conversion and molecular weight of polymer, such as polymerization time, temperature, monomer/catalyst ratio, and solvent, were examined. The results indicated that polymerization was rapid, with monomer conversions reaching 100% within 1 h, and the conformation of L-LA was retained. The structure of the block copolymer of CL/L-LA was characterized by NMR and differential scanning calorimetry. The morphological changes during crystallization of poly(caprolactone) (PCL)-b-P(L-LA) copolymer were monitored with real-time hot-stage atomic force microscopy (AFM). The effect of temperature on the morphological change and crystallization behavior of PCL-b-P(L-LA) copolymer was demonstrated through AFM observation.