Polymer-supported metallocene catalysts for ethylene polymerisation: Characterisation and catalytic studies

A series of polymer-supported unbridged metallocene dichloride catalysts, Cp″CpMCl₂ (where Cp″ = C₅Me₄H and M = Ti or Zr) have been prepared. These catalysts have been characterised in detail and have shown promising activity in ethylene polymerisation under extremely mild conditions.     

Synthesis and Structure of New Dimeric Cyclopentadienyl Titanium Fluorine–Oxygen Systems: [Cp*TiF(μ-F)(μ-OPOPh2)]2, [Cp*TiF(μ-F)(μ-OSO2-p-C6H4Me)]2 and [Cp*TiF2(μ-OMe)]2

The reactions of Cp*TiF₃ with Me₃SiOPOPh₂, Me₃SiOSO₂-p-C₆H₄Me, and Al(OMe)₃ resulted in the formation of the dimers [Cp*TiF(μ-F)(μ-OPOPh₂)]₂ 1 , [Cp*TiF(μ-F)(μ-OSO₂-p-C₆H₄Me)]₂ 2 , and [Cp*TiF₂(μ-OMe)]₂ 3 , respectively, in good yields. In contrast to the formation of 3 , Cp*TiF₃ reacts with Al(OH)₃ to afford the known tetramer [Cp*TiF(μ-O)]₄ 4 . The structures of 1–3 have been determined by X-ray crystallography; compounds 1 and 3 crystallize in the monoclinic space group P2₁/c and compound 2 in the monoclinic space group P2/n. Compound 1 is the first example of a dimeric Cp*-titanium phosphinate containing a fluorine ligand. The core of the dimeric structure of both 1 and 2 consists of two Ti atoms bridged by two fluorine atoms and two bidentate groups. In contrast, the dimeric structure of 3 consists of two Ti atoms bridged only by two methoxy groups. An equilibrium of isomers of 1 and 2 has been observed in solution by ¹H and ¹⁹F NMR. The ¹⁹F NMR spectra of 1–3 are discussed in detail.     

Cyclopentadienylation of allyl-chlorine enriched PVC and degradation thereof

Summary Pendant cyclopentadienyl groups (Cp) have been introduced by treatment with Me₂CpAl into poly(vinyl chlorides) the allyl chlorine contents of which was augmented by mild chemical dehydrochlorination [PVC(A)]. Heating the cyclopentadienylated products [PVC(A)-Cp] led to gels, most likely by Diels-Alder addition, because the networks could be broken by strong dieno-philes, e.g., maleic anhydride. The thermal stability of PVC(A)'s was improved upon Me₂CpAl treatment due to the substitution of thermally unstable allylic chlorines by Cp groups. The thermooxidative stability of PVC(A)-Cp was reduced relative to that of PVC(A) on account of the high oxidizability of Cp groups in the resin.     

Binuclear rhodium(III) and iridium(III) monoselenocarboxylates: Synthesis,spectroscopy and structure of an ortho-metallated iridium complex featuring an IrCCC(μ-Se) chelate ring

Monoselenocarboxylate–bridged binuclear complexes of Rh^III and Ir^III, [(Cp1MCl)₂(μ-SeCOAr)₂] (1) (M = Rh or Ir; Cp1 = pentamethylcyclopentadienyl; Ar = Ph, C₆H₄Me–4), have been isolated either by the reaction between [Cp1₂M₂(μ-Cl)₂Cl₂] with KSeCOAr in acetonitrile or by treatment of [Cp1MCl(solvent)₂][PF₆] with KSeCOAr in acetone. The novel binuclear complexes, [Cp1IrCl(μ-SeCOAr)(κ²-SeCOC₆H₃R–)IrCp1] (2) (R = H or Me-4) with ortho-metallation at one of the iridium centres have been isolated following the use of excess AgPF₆. The single crystal structure of [Cp1IrCl(μ-SeCOC₆H₅)(κ²-SeCOC₆H₄–)IrCp1] (2a) exhibits two phenylcarboselenolate moieties situated in syn fashion with respect to the “Ir₂Se₂” plane, one of which leans towards the metal centre in order to undergo ortho-metallation after iridium–chlorine bond dissociation.     

Synthesis and structure of the cubane type [Fe2Sb(CO)5(η5-C5H5)]4 cluster

The [Fe₂Sb(CO)₅Cp]₄ (Cp=η⁵-C₅H₅) cluster has been obtained by the thermolysis of [Et₄N][{Fe(CO)₄}₂{Fe(CO)₂Cp}SbI]. The structure of the [Fe₂Sb(CO)₅Cp]₄·2toluene solvate has been determined by X-ray analysis. The cluster contains the cubane [Fe₄Sb₄] core. Each Sb serves as a μ₄-ligand between three iron atoms of the core and one of a terminal [Fe(CO)₂Cp] group.     

Dynamic relaxation characteristics of crosslinked poly(ethylene oxide) copolymer networks: Influence of short chain pendant groups

The dynamic relaxation characteristics of short-branch rubbery amorphous networks prepared by the photopolymerization of poly(ethylene glycol) diacrylate [PEGDA] crosslinker have been investigated using dynamic mechanical analysis and broadband dielectric spectroscopy. Copolymerization with low molecular weight acrylates was used to control effective crosslink density in the networks and led to the insertion of ethylene oxide pendant groups along the network backbone. Substantial differences in the sub-glass and glass-rubber relaxation properties of the copolymers were observed as a function of pendant length and the nature of the pendant terminal group (e.g., -OH vs. -OCH₃); the results are compared with prior studies on model copolymers containing longer, more flexible side branches.     

Umsetzungen des Pentamethylcyclopentadienyl‐Halbsandwichkomplexes Cp*Ta(CO)4 mit Chlor,Brom und Iod

The reaction of Cp*Ta(CO)₄ ( 1 ) (Cp* = η⁵‐pentamethylcyclopentadienyl, η⁵‐C₅Me₅) with chlorine leads to Cp*TaCl₄ ( 2a ), whereas the corresponding reactions with bromine or iodine give the oxo‐bridged complexes [Cp*TaX₃]₂(μ‐O) (X = Br ( 3b ), I ( 3c )). The oxygen atom apparently stems from a carbonyl ligand. In the presence of air, the binuclear complexes 3a , b are converted into mononuclear Cp*Ta(O)X₂ ( 4b , c ). The X‐ray structural determination of [Cp*TaBr₃]₂(μ‐O) ( 3b ) confirms a linear Ta–O–Ta bridge with a Ta–O distance of 190,4(1) pm.     

N‐Alkylation of Amines with Alcohols Catalyzed by a Water‐Soluble Cp*Iridium Complex: An Efficient Method for the Synthesis of Amines in Aqueous Media

An efficient and environmentally benign catalytic system for the synthesis of various organic amines catalyzed by the water‐soluble and air‐stable (pentamethylcyclopentadienyl)‐iridium‐ammine iod‐ ide complex, [Cp*Ir(NH₃)₃][I]₂ (Cp*=pentamethylcyclopentadienyl), has been developed. A wide variety of secondary and tertiary amines were synthesized by the N‐alkylation reactions of theoretical equivalents of amines with alcohols in water under air without a base. The synthesis of cyclic amines was also achieved by the N‐alkylation of benzylamine with diols. Furthermore, the recycle use of the present water‐soluble Cp*Ir catalyst was accomplished.     

Crystallization analysis fractionation of ethene/1-hexene copolymers made with the MAO-activated dual-site (1,2,4-Me3Cp)2ZrCl2 and (Me5Cp)2ZrCl2 system

Different poly(ethene-co-1-hexene) samples with varying amounts of 1-hexene were characterized by crystallization analysis fractionation (Crystaf). The samples were synthesized with (1,2,4-Me₃Cp)₂ZrCl₂, (Me₅Cp)₂ZrCl₂, and a mixture of these two catalysts in a 1:1 molar ratio. In addition, preparative Crystaf was used to fractionate some of the samples made with the catalyst mixture into 1-hexene-rich and 1-hexene-poor fractions. These fractions were characterized by Crystaf, differential scanning calorimetry (DSC) and gel permeation chromatography (GPC), and compared with copolymers made under similar conditions using the individual catalysts. Both (1,2,4-Me₃Cp)₂ZrCl₂ and (Me₅Cp)₂ZrCl₂ produced copolymers with unimodal distribution of short chain branches (SCBD), as expected for single-site catalysts. The catalyst mixture produced copolymers with bimodal SCBDs when 0.38 mol/l or higher concentrations of 1-hexene were used. The high temperature peak results from crystallization of polymer chains with few comonomer units, and these are attributed to (Me₅Cp)₂ZrCl₂. The low temperature peak results from crystallization of polymer chains made by (1,2,4-Me₃Cp)₂ZrCl₂, and these chains contain many comonomer units. Direct evidence for relative activity enhancement of the (Me₅Cp)₂ZrCl₂ catalyst in the dual-site system was observed.     

Synthesis,structure and reactions of triply selenolate-bridged diiron complex [Cp*Fe(μ-SeMe)3FeCp*]

Two new iron–selenolate complexes [Cp*Fe(μ-SeMe)₃FeCp*] (Cp* = η⁵-C₅Me₅) (1) and [Cp*Fe(μ-SeMe)₃FeCp*][FeCl₃] (2) were prepared by the oxidative addition reaction of MeSeSeMe with [Cp*FeCl]₂ in 25% and 20% yields, respectively. In refluxing toluene, the methyl groups in the selenolate ligands of complex 1 were removed, affording a cubane cluster [Cp*₄Fe₄Se₄] (3) in 50% yield. Complex 1 was oxidized by HBF₄ to give [Cp*Fe(μ-SeMe)₃FeCp*][BF₄] (4), and the reverse reduction reaction occurred in the presence of CoCp₂.     

Random and block copolymers based on 4-methyl-1-pentene and 1-pentene

The zirconium acetamidinate catalyst {Cp*Zr(Me)₂[N(Et)C(Me)N(tBu)]} (Cp* = ?⁵-C₅Me₅) was used to synthesize both random and block copolymers based on 4-methyl-1-pentene (4M1P) and 1-pentene. The polymers have been characterized by NMR spectroscopy, SEC, DSC, high temperature HPLC and CRYSTAF. Unexpectedly, the yields and molecular weights decreased with increasing amounts of 1-pentene. The reason for this behavior is that 1-pentene occasionally undergoes 2,1-misinsertions trapping the catalyst in a dormant state. These 2,1-misinsertions do not seem to occur with the bulky 4M1P (branched α-olefin). Adding a small amount of ethylene reactivates the catalyst. Unlike most semi-crystalline polymers, the density of the crystalline phase of isotactic P4M1P can be lower than of the amorphous phase, when crystallized under very high pressures. To characterize this peculiar behavior of 4M1P-based polymers, various samples have been subjected to Pressure-Volume-Temperature (PVT) measurements. While the P4M1P homopolymers and block copolymers show the expected decrease in specific volume upon crystallization, the 4M1P-rich random copolymers proved not to vary in specific volume under the same conditions.     

Effects of monomer and ether structure on metal-free living cationic polymerization of various vinyl ethers using hydrogen chloride with ether

A highly effective initiating system has been achieved for living cationic polymerization of vinyl ethers consisting of HCl alone without Lewis acid. This system is a facile metal-free living cationic polymerization using no HCl/Lewis acid but the already adopted complex HCl·Et₂O. In this study, we investigated the effects of a monomer and ether structure on the polymerization behavior. The monomers are classified into three kinds of monomers: alkyl vinyl ether, vinyl ether with electron-donating groups in the pendant, and vinyl ether with bulky group next to the electron-donating substituent in the pendant. The HCl·Et₂O systems were applicable for the polymerizations of all vinyl ethers used. However the structure around electron-donating groups in the pendant of monomer affected the polymerizations rate and induction period. The initiation reactions can be successfully achieved using ether effectively dissociating HCl, especially symmetrical ether.     

Synthesis and characterization of nickel(II) and copper(II) complexes with a tetramethyltetraaza macrocycle containing 2-pyridylmethyl pendant arms

The complexes [Ni(L²)](ClO₄)₂·H₂O (1) and [Cu(L²)]Cl₂·4H₂O (2) have been synthesized and characterized by X-ray crystallography, electronic absorption and cyclic voltammetry. The crystal structure of 1 reveals a distorted octahedral geometry with four nitrogen atoms of the macrocycle and two nitrogen atoms of the pendant pyridylmethyl groups. The structure of 2 shows that the complex is centrosymmetric and the metal center has a tetragonally distorted octahedral environment. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the presence of the pendant arms.     

Detection of sub-glass transition events in amorphous polymers using differential scanning calorimetry: 3. Further observations on polymers containing pendant cycloalkyl rings

Heat capacity (C_p) contributions have been calculated from the partition function which describes the conformational energies of cycloalkyl rings containing from 9 to 12 carbons. The magnitude of these contributions depends on the number of conformations available to the ring system, and is a maximum for cyclodecane. The heat capacity has been measured as a function of temperature for two dicycloalkyl itaconate polymers, one containing pendant cyclodecyl rings, and the other pendant cyclododecyl rings. In the case of the former polymer an inflection in the C_pT curve is observed below the glass transition temperature. The experimental values associated with this inflection correlate with the calculated contribution from the conformational energies of the cyclodecyl rings, and this supports our assignment of the molecular origin of glassy state relaxations in such polymers. Any similar contributions to the glassy state heat capacities of the other polymers in the series are below the levels of detection of our present equipment.     

Ruthenium‐Catalyzed O‐Allylation of Phenols from Allylic Chlorides via Cationic [Cp*(η3‐allyl)(MeCN)RuX][PF6] Complexes

The [Cp*(MeCN)₃Ru(II)][PF₆] complex is an efficient catalyst precursor for the O‐allylation of phenols with allylic chlorides in the presence of K₂CO₃ under mild conditions. This ruthenium precursor affords branched allyl aryl ethers according to a regioselective reaction, which contrasts with the uncatalyzed nucleophilic substitution from the same substrates. Stable (η³‐allyl)Ru(IV) cationic complexes resulting from the reaction of [Cp*(MeCN)₃Ru][PF₆] with allylic halides were identified as intermediate catalytic species. An X‐ray structure determination of the complex [Cp*(MeCHCHCH₂)(MeCN)RuBr][PF₆] disclosed an (endo‐trans‐MeCHCHCH₂) allylic ligand. The structural information obtained from the study of Cp*(allyl)Ru(IV) complexes indicated that electronic effects at the coordinated allylic ligand likely account for the better regioselectivity obtained from cinnamyl chloride as compared to aliphatic allylic chlorides.     

Photoresponsive electrode coated with bilayer membranes of polymer pendant Ru(bpy)2+3 complex and viologen

A new type of photodiode was proposed based on photochemical electron transfer occurring between bilayer membranes of polymer pendant Ru(bpy)²⁺₃ complex and pendant viologen. A bilayer system composed of a graphite electrode coated with polymer pendant Ru(bpy)²⁺₃ as inner layer in contact with the electrode and with polymer pendant viologen as outer layer induced photocurrent. The cathodic photocurrent was much higher than that induced by a monolayer system composed of mixture. The presence of O₂ scarcely affected the cathodic photocurrent induced by the bilayer system, but enhanced that of the monolayer system by 46 times.     

Novel ionenes with allyl pendant groups

Summary Novel ionenes with allyl pendant groups have been synthesized by condensation of N,N'- bisallylpiperazine with organic dihalides such as 1,4-dichlorobutane, 1,6-dibromohexane and 1,4-dichloromethylbenzene. The polymers are readily soluble in water and have low molecular weights. The structure of the ionenes has been identified by spectroscopic techniques. The concentrated aqueous solutions of the resulting ionenes can be crosslinked by t-butylhydroperoxide as a radical initiator to give transparent hydrogels. The ionenes also act as an crosslinking agent in copolymerization with high concentrations of acrylic acid in the presence of K₂S₂O₈ as a radical initiator in water at 65°C. Received: 29 July 1999/Revised version: 28 October 1999/Accepted: 28 October 1999     

Siloxane-poly(Methylmethacrylate) amphoteric blends

Poly([4-(methacryloyloxy) butyl]pentamethyldisiloxane), PMBPD, has been prepared for the first time. At the weight average molecular weight of 55,900, it is a clear, viscous liquid with a glass transition temperature, T_g, of 236K. Copolymers with methylmethacrylate have also been prepared. The homo-and copolymers, all of which have methacrylate backbones with pendant siloxane groups, were blended with poly(methyl-methacrylate), PMMA. Using the existence of a single T_g as a definition of miscibility, it was found that blends of either PMMA or PMBPD with random copolymers are miscible. However, in spite of a clear appearance, the blend of the two horriopolymers were found to have two distinct T_gs.     

2-氨基-5-(对-甲氧基苯基)-1,3,4-噻二唑稀土金属有机配合物的合成及表征

２－氨基－５－（对－甲氧基苯基）－１,３,４－噻二唑（以ＬＨ表示）与等摩尔三茂基稀土化合物反应,合成了六种文献中未见报道的稀土金属有机配合物Ｃｐ２ＬｎＬ（Ｃｐ＝η５－Ｃ５Ｈ５;Ｌｎ＝Ｙｂ,Ｔｍ,Ｅｒ,Ｈｏ,Ｄｙ,Ｎｄ）。这些配合物均经元素分析、红外光谱及质谱表征。从有关的数据推测出这类化合物可能的分子结构。     

Copolymerization of ethylene and 1‐decene by metallocenes: Direct comparison of Me2C(Cp)(Flu)ZrMe2 with Et(Cp)(Flu)ZrMe2

Copolymerizations of ethylene with 1‐decene have been carried out by using two syndiospecific metallocenes synthesized by modifying the bridge: highly syndiospecific isopropylidene(1‐η⁵‐cyclopentadienyl)(1‐η⁵‐fluorenyl)‐dimethylzirconium (Me₂C(Cp)(Flu)ZrMe₂, 1 ) and less syndiospecific (1‐fluorenyl‐2‐cyclopentadienylethane)‐dimethylzirconium (Et(Cp)(Flu)ZrMe₂, 2 ), in the presence of [Ph₃C][B(C₆F₅)₄] as a cocatalyst. The ethano bridged 2 compound of smaller dihedral angle showed much higher activity than 1 compound. The catalytic activities of the two compounds were enhanced about twice when a suitable amount of 1‐decene comonomer is present in the feed. The compound 1 showed better comonomer reactivity than 2 . The properties (T_m, density, and crystallinity) of copolymers seem not to be affected by the type of bridge of the metallocenes, and mainly depend on 1‐decene content in the copolymer.