Ethylene polymerization by 3‐oxa‐pentamethylene bridged asymmetric dinuclear titanocene/MAO system

An asymmetric 3‐oxa‐pentamethylene bridged dinuclear titanocenium complex (CpTiCl₂)₂(η⁵‐η⁵‐C₉H₆(CH₂CH₂OCH₂CH₂)C₅H₄) ( 1 ) has been prepared by treating two equivalents of CpTiCl₃ with the corresponding dilithium salts of the ligand C₉H₇(CH₂CH₂OCH₂ CH₂)C₅H₅. The complex 1 was characterized by ¹H‐, ¹³C‐NMR, and elemental analysis. Homogenous ethylene polymerization catalyzed using complex 1 has been conducted in the presence of methylaluminoxane (MAO). The influences ofreaction parameters, such as [MAO]/[Cat] molar ratio, catalyst concentration, ethylene pressure, temperature, and time have been studied in detail. The results show that the catalytic activity and the molecular weight (MW) of polyethylene produced by 1 /MAO decrease gradually with increasing the catalyst concentration or polymerization temperature. The most important feature of this catalytic system is the molecular weight distribution (MWD) of polyethylene reaching 12.4, which is higher than using common mononuclear metallocenes, as well as asymmetric dinuclear titanocene complexes like [(CpTiCl₂)₂(η⁵‐η⁵‐C₉H₆(CH₂)_nC₅H₄)] (n = 3, MWD = 7.31; n = 4, MWD = 6.91). The melting point of polyethylene is higher than 135°C, indicating highly linear and highly crystalline polymers. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Ethylene polymerization using an asymmetric dinuclear titanocene catalyst carrying a novel 3-oxa-pentamethylene bridge

The asymmetric 3-oxa-pentamethylene bridged dinuclear titanocenium complex (CpTiCl₂)₂ (η⁵-C₉H₆(CH₂CH₂ OCH₂CH₂)-η⁵-C₅H₃ CH₃) (1) has been prepared, characterized by ¹H NMR spectroscopy and elemental analysis, and after activation with MAO tested as a homogenous catalyst for the polymerization of ethylene. The results show that the catalytic activity of 1 as well as the molecular weight of the produced polyethylene are higher than those using the alkylidene bridged asymmetric dinuclear metallocenes (CpTiCl₂)₂ (η⁵-C₉H₆(CH₂) _n-η⁵-C₅H₄), n = 3 (4), 4 (5). The molecular weight distribution of polyethylene produced with 1/MAO reaches 11.00 and the HT-GPC curve shows a bimodal distribution. The melting point of the polyethylene obtained by 1/MAO is higher than 135 °C and the ¹³C NMR spectrum of PE shows only one strong signal at 30 ppm for the methylene units indicating a highly linear and crystalline polymer.     

Ethylene polymerization using an asymmetric dinuclear titanocene catalyst carrying a novel 3-oxa-pentamethylene bridge

The asymmetric 3-oxa-pentamethylene bridged dinuclear titanocenium complex (CpTiCl₂)₂ (η⁵-C₉H₆(CH₂CH₂ OCH₂CH₂)-η⁵-C₅H₃ CH₃) (1) has been prepared, characterized by ¹H NMR spectroscopy and elemental analysis, and after activation with MAO tested as a homogenous catalyst for the polymerization of ethylene. The results show that the catalytic activity of 1 as well as the molecular weight of the produced polyethylene are higher than those using the alkylidene bridged asymmetric dinuclear metallocenes (CpTiCl₂)₂ (η⁵-C₉H₆(CH₂) _n-η⁵-C₅H₄), n = 3 (4), 4 (5). The molecular weight distribution of polyethylene produced with 1/MAO reaches 11.00 and the HT-GPC curve shows a bimodal distribution. The melting point of the polyethylene obtained by 1/MAO is higher than 135 °C and the ¹³C NMR spectrum of PE shows only one strong signal at 30 ppm for the methylene units indicating a highly linear and crystalline polymer.     

Ethylene polymerization by phenylenedimethylene‐bridged homobinuclear zirconocene/methylaluminoxane systems

In the presence of methylaluminoxane (MAO), ethylene polymerization was successfully performed with homobinuclear zirconocene complexes {[(C₅H₅)ZrCl₂](C₅H₄CH₂ C₆H₄CH₂C₅H₄)[(C₅H₅)ZrCl₂]; 3o , 4m , and 5p }, which were prepared conveniently by the reaction of disodium(phenylenedimethylene)dicyclopentadienide [C₆H₄(CH₂C₅H₄Na)₂] with 2 equiv of (N⁵‐Cyclopentadienyl)trichlorozirconium dimethoxyethane (CpZrCl₃(DME)) in tetrahydrofuran and characterized by ¹H‐NMR and elemental analysis. The effects of the polymerization parameters, such as the temperature, time, concentration of the catalyst, MAO/catalyst molar ratio, and isomeric difference of the homobinuclear metallocene complexes 3o , 4m , and 5p were studied in detail. The results showed that all three catalytic systems had moderate activities in ethylene polymerization and afforded polyethylene with relatively broad polydispersities. The catalytic activity of 4m was somewhat higher than that of 3o and 5p but lower than that of 4,4′‐bis(methylene)biphenylene‐bridged zirconocene catalysts; this indicated that the distance between the two metal centers was too short in comparison with a 4,4′‐bis(methylene)biphenylene bridge to increase the catalytic activity. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Novel diphenyl thioether‐bridged binuclear metallocenes of Ti and Zr for synthesis of polyethylene with broad molecular weight distribution

Two diphenyl thioether‐bridged binuclear metallocenes of Ti and Zr, [(C₅H₅)Cl₂MC₅H₄CH₂(p‐C₆H₄)]₂S [M = Ti (1) and Zr (2)], have been synthesized by treating the dilithium salts of the corresponding ligand [(C₅H₅CH₂(p‐C₆H₄)]₂S with two equivalents of C₅H₅TiCl₃ and C₅H₅ZrCl₃(DME), respectively, in toluene at 0°C. Both new complexes have been characterized by ¹H‐NMR spectroscopy and elemental analysis. Homogeneous ethylene polymerization using both complexes was performed in the presence of methylaluminoxane (MAO). The influences of molar ratio of [MAO]/[Cat], concentration of the catalysts, time, and temperature have been studied systematically. The catalytic activity of 1 is higher than that of the corresponding oxygen‐bridged catalyst [(C₅H₅)Cl₂TiC₅H₄CH₂(p‐C₆H₄)]₂O. The catalytic activity of 2 is at least two times higher than that of 1 under any tested polymerization conditions. The melting points of polyethylene (PE) produced by 1 and 2 are higher than 130°C, indicating a highly linear and highly crystalline PE. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Metallkomplexe mit biologisch wichtigen Liganden. CXXIII. Darstellung von Isophthaloyl‐ und Terephthaloyl‐di‐[(β,γ,δ)‐amino‐α‐aminocarboxylat]‐verbrückten zweikernigen Ruthenium‐, Rhodium‐ und Iridium‐Halbsandwich‐Komplexen

The reaction of the Cu(II) bis N,O‐chelate‐complexes of L‐2,4‐diaminobutyric acid, L‐ornithine and L‐lysine {Cu[H₂N–CH(COO)(CH₂)_nNH₃]₂}²⁺(Cl^–)₂ (n = 2–4) with terephthaloyl dichloride or isophthaloyl dichloride gives the polymeric complexes {‐OC–C₆H₄–CO–NH–(CH₂)_n–CH(nh₂)(COO)Cu(OOC)(NH₂)CH–CH₂)_n–NH‐}_x 1 – 5 . From these the metal can be removed by precipitation of Cu(II) with H₂S. The liberated ω,ω′‐N,N′‐diterephthaloyl (or iso‐phthaloyl)‐diaminoacids 6 – 10 react with [Ru(cymene)Cl₂]₂, [Ru(C₆Me₆)Cl₂]₂, [Cp*RhCl₂]₂ or [Cp*IrCl₂]₂ to the ligand bridged bis‐amino acidate complexes [L_n(Cl)M–(OOC)(NH₂)CH–(CH₂)_nNH–CO]₂–C₆H₄ 11 – 14 .     

Dimerization of Terminal Arylalkynes in Aqueous Medium by Ruthenium and Acid Promoted (RAP) Catalysis: Acetate‐ Assisted (sp)C?(sp2)C Bond Formation

The hexamethylbenzene ruthenium(II) dimer [{RuCl(μ‐Cl)(η⁶‐C₆Me₆)}]₂ (5 mol%), tested among a series of ruthenium(II) and ruthenium(IV) complexes, represents an efficient precatalyst source for the dimerization of terminal arylalkynes ArCCH [Ar=C₆H₅, 3,4,5‐(OMe)₃C₆H₂, 4‐MeOC₆H₄, 2‐MeOC₆H₄, 4‐MeC₆H₄, 2,4,5‐Me₃C₆H₂, 4‐BrC₆H₄, 4‐ClC₆H₄, 4‐FC₆H₄, 4‐HC(O)C₆H₄, 4‐CH₂CHC₆H₄, 3‐NCC₆H₄, 4‐O₂NC₆H₄, 4‐EtO₂C‐(CH₂)₃OC₆H₄, 4‐HO(CH₂CH₂O)₃C₆H₄, 3‐HO(CH₂CH₂O)₃‐C₆H₄] in acetic acid/water mixture (1:1, v/v). The reactions proceed for 24 h at room temperature under heterogeneous conditions and afford the dimeric enyne derivatives (E)‐Ar CHCH CC Ar in high yields and stereoselectivity. The preformed acetato complex [RuCl(η⁶‐C₆Me₆)(κ²‐OAc)] catalyzes the dimerization of phenylacetylene under analogous conditions, with rapid substrate conversion. The presence of cosolvents of acetic acid different from water reduces dramatically the efficiency and selectivity of the reaction. The aqueous medium facilitates the activation stage of the precatalyst by assisting the splitting of the ruthenium dimer. The addition or generation in situ of acetate salts results in shorter reactions times (0.5–3 h) and excellent yields, due to the rapid formation of active acetato complexes. Circumstantial evidence indicates that the π‐bound alkyne molecule is activated by intramolecular proton abstraction. This is currently the most efficient, E‐selective and wide‐scope catalytic system for the alkyne dimerization reaction in protic aqueous media.     

Synthesis of pyrrole-bridged constrained geometry complexes and their application for olefin polymerization

In this article, four constrained geometry complexes 4a [(η⁵-C₅H₄)CH₂(α-C₄H₃N)]Ti(NMe₂)₂, 7a [(η⁵-C₉H₆)CH₂(α-C₄H₃N)]Ti(NMe₂)₂, 4b [(η⁵-C₅H₄)CH₂(α-C₄H₃N)]Zr(NEt₂)₂, 7b [(η⁵-C₉H₆)CH₂(α-C₄H₃N)]Zr(NEt₂)₂ with pyrrole-bridged fragment were synthesized and characterized by ¹H NMR, ¹³C NMR, MASS, and EA. When combined with MAO, complex 4b given the highest activity, the activity of copolymerizing ethylene and 1-hexene reached 2.48 × 10⁶ g polymer/mol·M·h. The effects of temperature, pressure, and ratio of Al/Metal on the polymerization reaction and properties of polymers had been investigated. The polymers with these complexes were characterized by ¹³C NMR and DSC, and the results shown that polymer with 4a had the highest α-olefin incorporation, the incorporation of 1-hexene reached up to 9.81 mol%, and the 1-octene was 8.84 mol%. Actually, there was no [HH] or [OO] sequence in the copolymer, according to the formula of reactivity ratio, rE • rH = 0, all these results suggested that the copolymerization mode is alternating copolymerization. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48620.     

Asymmetric 1,3‐Dipolar Cycloaddition Reaction between α,β‐Unsaturated Aldehydes and Nitrones Catalyzed by Well‐Defined Iridium or Rhodium Catalysts

Reaction of the complexes (S_M,R_C)‐[(η⁵‐C₅Me₅)M{(R)‐Prophos}(H₂O)](SbF₆)₂ (M=Rh, Ir) with α,β‐unsaturated aldehydes diastereoselectively gave complexes (S_M,R_C)‐[(η⁵‐C₅Me₅)M{(R)‐Prophos}(enal)](SbF₆)₂ which have been fully characterized, including an X‐ray molecular structure determination of the complex (S_Rh,R_C)‐[(η⁵‐C₅Me₅)Rh{(R)‐Prophos}(trans‐2‐methyl‐2‐pentenal)](SbF₆)₂. These enal complexes efficiently catalyze the enantioselective 1,3‐dipolar cycloaddition of the nitrones N‐benzylideneaniline N‐oxide and 3,4‐dihydroisoquinoline N‐oxide to the corresponding enals. Reactions occur with excellent regioselectivity, perfect endo selectivity and with enantiomeric excesses up to 94 %. The absolute configuration of the adduct 5‐methyl‐2,3‐diphenylisoxazolidine‐4‐carboxaldehyde was determined through its (R)‐(−)‐α‐methylbenzylamine derivative.     

Investigation of Dynamic Intra‐ and Intermolecular Processes within a Tether‐Length Dependent Series of Group 4 Bimetallic Initiators for Stereomodulated Degenerative Transfer Living Ziegler–Natta Propene Polymerization

The series of bimetallic complexes, [(η⁵‐C₅Me₅)Zr(Me)₂]₂ [N(t‐Bu)C(Me)N (CH₂)_n NC(Me)N(t‐Bu)] 3 (n=8), 4 (n=6), and 5 (n=4) were prepared in high yield through a simple, one‐pot synthesis involving 2 equiv. of in situ generated (η⁵‐C₅Me₅)Zr(Me)₃ and the corresponding bis‐carbodiimide, (t‐Bu)NCN (CH₂)_n NCN(t‐Bu). Compounds 3 – 5 were found to be highly isoselective for the living Ziegler–Natta polymerization of propene upon 100% activation using 2 equiv. of the borate co‐initiator, [PhNHMe₂] [B(C₆F₅)₄] ( 2 ), with the degree of stereoselectivity decreasing slightly as the two metal centers are brought closer together [cf., 3 (σ=0.92)> 4 (σ=0.91)> 5 (σ=0.89)]. Under conditions of sub‐stoichiometric activation by 2 , all three bimetallic initiators, 3 – 5 , were found to engage in degenerative transfer living Ziegler–Natta polymerization involving rapid and reversible methyl group transfer between active, (cationic) and dormant, (neutral) methyl, polymeryl zirconium centers. Under these conditions, the frequency of mr triad stereoerror incorporation into the polypropene (PP) microstructure decreases as the two metal centers are brought closer together as a result of increasing barriers for metal‐centered epimerization within the neutral metal site due to correspondingly greater non‐bonded steric interactions vis‐à‐vis mononuclear 1 .     

Alkyne Metatheses in Transition Metal Coordination Spheres: Convenient Tungsten‐ and Molybdenum‐Catalyzed Syntheses of Novel Metallamacrocycles

Reactions of (CO)₅Re(Br), (η⁵‐C₅H₅)Ru(Cl)(PPh₃)₂, and [Pt(μ‐Cl)(C₆F₅)(S(CH₂CH₂‐)₂)]₂ with the alkyne‐containing phosphine Ph₂P(CH₂)₆C≡CCH₃ give the bis(phosphine) complexes fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 5 ), (η⁵‐C₅H₅)Ru(Cl)(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 6 ), and trans‐(Cl)(C₆F₅)Pt(Ph₂P(CH₂)₆C≡CCH₃)₂ ( 7 ). Alkyne metatheses with the catalyst (t‐BuO)₃W(≡C‐t‐Bu) (10–15 mol %, chlorobenzene, 80 °C) give the seventeen‐membered metallamacrocycles fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 8 ), (η⁵‐C₅H₅)Ru(Cl)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 9 ), and trans‐(Cl)(C₆F₅)Pt(PPh₂(CH₂)₆CC(CH₂)₆P Ph₂) ( 10 ). ³¹P NMR analyses show 90–75% conversions to 8 – 10 (59–47% isolated after chromatography). The identity of 8 was confirmed by a crystal structure, and 10 was hydrogenated over Pd/C to fac‐(CO)₃Re(Br)(Ph₂P(CH₂)₆CC(CH₂)₆P Ph₂) ( 12 , 87%), which was crystallographically characterized earlier. A catalyst derived from Mo(CO)₆/4‐chlorophenol effects a slower conversion of 7 to 10 at 140 °C. In the case of 5 , a mer, trans isomer of 8 is isolated ( 11 , 44%), as established by NMR and IR data. In 10 – 12 , the diphosphines span trans positions. These results, together with previous examples involving group VIII metallocenes, establish the wide viability of the title reaction.     

Anticancer Potential of (Pentamethylcyclopentadienyl)chloridoiridium(III) Complexes Bearing κP and κP,κS‐Coordinated Ph2PCH2CH2CH2S(O)xPh (x=0–2) Ligands

Iridium(III) complexes of the type [Ir(η⁵‐C₅Me₅)Cl₂{Ph₂PCH₂CH₂CH₂S(O)_xPh‐κP}] (x=0–2; 1 – 3 ) and [Ir(η⁵‐C₅Me₅)Cl{Ph₂PCH₂CH₂CH₂S(O)_xPh‐κP,κS}][PF₆] (x=0–1; 4 and 5 ) with 3‐(diphenylphosphino)propyl phenyl sulfide, sulfoxide, and sulfone ligands Ph₂PCH₂CH₂CH₂S(O)_xPh were designed, synthesized, and characterized fully, including X‐ray diffraction analyses for complexes 3 and 4 . In vitro studies against human thyroid carcinoma (8505C), submandibular carcinoma (A253), breast adenocarcinoma (MCF‐7), colon adenocarcinoma (SW480), and melanoma (518A2) cell lines provided evidence for the high biological potential of the neutral and cationic iridium(III) complexes. Neutral iridium(III) complex 5 proved to be the most active, with IC₅₀ values up to about 0.1 μM , representing activities of up to one order of magnitude higher than cisplatin. Using 8505C cells, apoptosis was shown to be the main mechanism through which complex 5 exerts its tumoricidal action. The described iridium(III) complexes represent potential leads in the search for novel metal‐based anticancer agents.     

Influence of Electrostatic Interactions on Complexes with Short O···O Hydrogen Bonds in Basic Salts of Pyridine Betaines and Acid Salts of ω-Phenyloalkanocarboxylic Acids

The isostructural complexes [C₅H₅N⁺(CH₂)_nCOO]₂HX and [C₆H₅(CH₂)_nCOO]₂HK (n = 1–4), which differ in their counterions and charge on the ring, were synthesized, and their powder FT-IR spectra analyzed. All complexes containing a charged pyridine ring are of Hadži type iii, characterized by an intense broad (continuum) absorption below 1600 cm⁻¹ typical of a short-strong hydrogen bond (SSHB) with a delocalized proton and a single vC=O band. The positively charged nitrogen atoms interact electrostatically with the X⁻ ion and, additionally, with one of the oxygen atoms of the carboxylic group, producing a more or less symmetric environment of the H-bonded proton, and stabilizing the SSHB. The broad absorption of [C₆H₅CH₂COO]₂HK is very similar to that of other pyridine complexes. Upon addition of methylene groups the broad absorption moves to higher wavenumbers, the O···O distance is elongated, and the H-bonded proton becomes more localized. In the spectrum of [C₆H₅(CH₂)₄COO]₂HK the vC=O and v_asCOO bands were found at 1704 and 1641 cm⁻¹, respectively, which shows that the H-bonded proton is asymmetrically located. The observed variation of absorption with the number of CH₂ groups reflects changes of contacts between the K⁺ ion and COO⁻ groups.     

Synthesis,Surface and Antimicrobial Activities of Novel Cationic Gemini Surfactants

A series of novel cationic gemini surfactants [C_nH_2n+1–O–CH₂–CH(OH)–CH₂–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? [ 3a (n = 12), 3b (n = 14) and 3c (n = 16)] having a 2‐hydroxy‐1,3‐oxypropylene group [?CH₂–CH(OH)–CH₂–O–] in the hydrophobic chain have been synthesized and characterized. Their water solubility, surface activity, foaming properties, and antibacterial activity have been examined. The critical micelle concentration (CMC) values of the novel cationic gemini surfactants are one to two orders of magnitude smaller than those of the corresponding monomeric surfactants. Furthermore, the novel cationic gemini surfactants have better water solubility and surface activity than the comparable [C_nH_2n+1–N⁺(CH₃)₂–(CH₂)₂]₂·2Br^? (n‐4‐n) geminis. The novel cationic gemini surfactants 3a and 3b also exhibit good foaming properties and show good antibacterial and antifungal activities.     

Synthesis of pentavalent imidovanadium complexes and their catalyses for the polymerization of ethylene and propylene

Imidovanadium complexes with cyclopentadienyl (Cp) ligands—(Cp)V(?NC₆H₄Me‐4)Cl₂ (1), (Cp)V(?N^tBu)Cl₂ (2), and (^tBuCp)V(?N^tBu)Cl₂ (3; ^tBuCp = tert‐butylcyclopentadienyl)—were synthesized through the reaction of imidovanadium trichloride with (trimethylsilyl)cyclopentadiene derivatives. The molecular structure of 3 was determined by X‐ray crystallography. The monocyclopentadienyl complex 1 exhibited moderate activity in combination with methylaluminoxane [MAO; 10.3 kg of polyethylene (mol of V)^?1 h^?1 atm^?1], whereas similar complexes with bulky ^tBu groups, 2 and 3, were less active. (2‐Methyl‐8‐quinolinolato)imidovanadium complexes, V(?NR)(O ?N)Cl₂ (R = C₆H₃ⁱPr₂‐2,6 (4) or n‐hexyl (5), O ?N = 2‐methyl‐8‐quinolinolato), were obtained from the reaction of imidovanadium trichloride with 2‐methyl‐8‐quinolinol. Upon activation with modified MAO, complex 4 showed moderate activities for the polymerization of ethylene at room temperature. The complex 5/MAO system also exhibited moderate activity at 0°C. The polyethylenes obtained by these complexes had considerably high melting points, which indicated the formation of linear polyethylene. Moreover, the 5/dried MAO system showed propylene polymerization activities and produced polymers with considerably high molecular weights and narrow molecular weight distributions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1008–1015, 2005     

Metal–metal interaction through CH2–CN bridge: synthesis and characterization of [CpM(L2)NCCH2Fc]PF6 complexes (Fc=ferrocenyl; L=1/2 dppe,PPh3; M=Fe,Ru)

The new complexes [CpM(L₂)NCCH₂Fc]PF₆ (M=Fe 1, Ru 2; Fc=ferrocenyl), have been prepared from reaction of CpM(L₂)X and the ligand Fc–CH₂CN 3 in methanol and in the presence of NH₄PF₆. The compounds were characterized by elemental analysis as well as spectroscopic methods. Electrochemical as well as near-IR measurements suggest a weak metal–metal interaction for the Fe(II)–Fe(III) complex. Hush parameters for this mixed-valence complex suggest a class II Robin–Day type with a moderate metal–metal interaction similar to that observed in the related pyridine bridged systems (η⁵-C₅H₅)Fe-η⁵-C₅H₄–C₅H₄N–ML_n. The unusual electron transfer through a insulating CH₂ group is the first such example for an asymmetric binuclear system.     

Polymerization of styrene using novel bispyrazolylimine dinickel (II)/methylaluminoxane catalytic systems

The polymerization of styrene with a series of bispyrazolylimine dinickel (II) complexes of bis‐2‐(C₃HN₂(R₁)₂‐3,5)(C(R₂) = N(C₆H₃(CH₃)₂‐2,6)Ni₂Br₄ (complex 1 : R₁ = CH₃, R₂ = Ph; complex 2 : R₁ = CH₃, R₂ = 2,4,6‐trimethylphenyl; complex 3 : R₁ = R₂ = Ph; complex 4 : R₁ = Ph, R₂ = 2,4,6‐trimethylphenyl) in the presence of methylaluminoxane (MAO) was studied. The influences of polymerization parameters such as polymerization temperature, Al/Ni molar ratio, reaction time, and catalyst concentration on catalytic activity and molecular weight of the polystyrene were investigated in detail. The influence of the bulkiness of the substituents on polymerization activity was also studied. All of the four catalytic systems exhibited high activity (up to 10.50 × 10⁵ gPS/(mol Ni h)) for styrene polymerization and provide polystyrene with moderate to low molecular weights (M_w = 4.76 × 10⁴–0.71 × 10⁴ g/mol) and narrower molecular weight distributions about 2. The obtained polystyrene was characterized by means of FTIR, ¹H‐NMR, and ¹³C‐NMR techniques. The results indicated that the polystyrene was atactic polymer. The analysis of the end groups of polystyrene indicated that styrene polymerization with bispyrazolylimine dinickel complexes/MAO catalytic systems proceeded through a coordination mechanism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Ruthenium Catalyzed Selective Regio‐and‐Mono‐Allylation of Cyclic 1,3‐Diketones Using Allyl Alcohols as Substrates

The new ruthenium‐sulfonate catalyst Ru(Cp*)(η³‐C₃H₅) (p‐CH₃C₆H₄SO₃)₂, (Cp*=pentamethylcyclopentadienyl), rapidly and regioselectively mono‐allylates dimedone to the branched products using substituted allyl alcohols as substrates, without acid, base or other additives, under relatively mild conditions. We consider the ruthenium sulfonate to be a “green” alternative in that it uses allyl alcohols as substrate, (rather than carbonates, acetates, etc.) and therefore does not waste the leaving group. The catalyst induces rapid double allylation of various 1,3‐diketones in high yield using allylic alcohol.     

Synthesis of high molecular weight copolymer of styrene and butadiene bearing high 1,4‐cis butadiene unit from copolymerization with CpTiCl3/methylaluminoxane catalyst

Copolymerization of styrene (St) and butadiene (Bd) with CpTiCl₃/methylaluminoxane (MAO) catalyst in the presence or absence of chloranil (CA) was investigated. The CpTiCl₃/MAO catalyst showed a high activity for the copolymerization of St with Bd. The 1,4‐cis contents in the Bd units for the copolymerization of St and Bd with the CpTiCl₃/MAO catalyst was observed, and the 1,4‐cis content was optimum at a MAO/Ti mole ratio of around 225. The effect of the polymerization temperature on the copolymerization was noted, as was the effect of the 1,4‐cis microstructure in the Bd units for the copolymerization of St and Bd. The addition of CA to the CpTiCl₃/MAO catalyst was found to influence the molecular weight of the copolymer. The high weight‐average molecular weight copolymer (M_w = ca. 50 × 10⁴) consisting of mainly a 1,4‐cis microstructure of Bd units (1,4‐cis = 80.0%) was obtained from the copolymerization with the CpTiCl₃/MAO catalyst in the presence of CA (CA/Ti mole ratio = 1) at 0°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2942–2946, 2003     

Structural characterization and thermal behaviour of block copolymers of polydimethylsiloxane and polyamide having trichlorogermyl pendant groups

Block copolymers having a pendant trichlorogermyl group as a part of polyamide segment? (CO? R′? CO? NH? Ar? NH? )_xCO? R′? CO? and polydimethylsiloxane of general formula [(? CO? R′? CO? HN? Ar? NH)_x? CO? R′? CO? NH(CH₂)₃SiO(CH₃)₂ ((CH₃)₂SiO)_ySi(CH₃)₂(CH₂)₃ NH? ]_n (where R′ = CH₂CH(GeCl₃), CH(CH₃)CH(GeCl₃), CH(GeCl₃)CH(CH₃); Ar = C₆H₄, (? C₆H₃? CH₃)₂, (? C₆H₃? OCH₃)₂, 2,5‐(CH₃)₂? C₆H₂, C₆H₄? O? C₆H₄) were prepared by a polycondensation reaction and characterized using CHN and Ge analysis, Fourier transform infrared (FTIR) and ¹H NMR spectroscopy, thermogravimetric analysis (TGA) and molecular weight determination. They have a lamellar structure with weight‐average molecular weight in the range 1.21 × 10⁵–4.79 × 10⁵ g mol^?1. These copolymers display two glass transition temperatures and have an average decomposition temperature of 489 °C. TGA, FTIR and gas chromatography/mass spectrometry studies indicate that degradation of these block copolymers results in carbon monoxide, oligomeric siloxanes and polyamide fragments. They are thermally stable due to the hydrogen bonded interlinked chains of polyamide, while they absorb water due to the presence of Ge? Cl bonding. Copyright © 2010 Society of Chemical Industry