Facile,Efficient Copolymerization of Ethylene with Bicyclic,Non‐Conjugated Dienes by Titanium Complexes Bearing Bis(β‐Enaminoketonato) Ligands

Copolymerizations of ethylene with 5‐vinyl‐2‐norbornene or 5‐ethylidene‐2‐norbornene under the action of various titanium complexes bearing bis(β‐enaminoketonato) chelate ligands of the type, [R¹NC(R²)CHC(R³)O]₂TiCl₂ ( 1 , R¹=Ph, R²=CF₃, R³=Ph; 2 , R¹=C₆H₄F‐p, R²=CF₃, R³=Ph; 3 , R¹=Ph, R²=CF₃, R³=t‐Bu; 4 , R¹=C₆H₄F‐p, R²=CF₃, R³=t‐Bu; 5 , R¹=Ph, R²=CH₃, R³=CF₃; 6 , R¹=C₆H₄F‐p, R²=CH₃, R³=CF₃), have been shown to occur with the regioselective insertion of the endocyclic double bond of the monomer into the copolymer chain, leaving the exocyclic vinyl double bond as a pendant unsaturation. The ligand modification strongly affects the copolymerization behaviour. High catalytic activities and efficient co‐monomer incorporation can be easily obtained by optimizing the catalyst structures and polymerization conditions.     

Notable Effects of Aluminum Alkyls and Solvents for Highly Efficient Ethylene (Co)polymerizations Catalyzed by (Arylimido)‐ (aryloxo)vanadium Complexes

The effects of both Al cocatalyst and solvent on catalytic activity in the ethylene polymerization by the (arylmido)(aryloxo)vanadium(V) complex, VCl₂(N‐2,6‐Me₂C₆H₃)(O‐2,6‐Me₂C₆H₃) ( 1 ), have been explored in detail. The activity of 5.84×10⁵ kg PE/mol V⋅h (TOF 2.08×10⁷ h⁻¹) has been achieved by 1 /EtAlCl₂ catalyst in CH₂Cl₂ at 0 °C, and the activity in toluene increased in the order: i‐Bu₂AlCl>EtAlCl₂>Me₂AlCl>Et₂AlCl> Et₂Al(OEt), AlEt₃, AlMe₃ (negligible activities). Both aluminum alkyl cocatalyst and solvent also affected the catalytic activity and the norbornene (NBE) incorporation in the ethylene/NBE copolymerization using complex 1 , whereas the NBE contents were not strongly affected by the kind of aryl oxide ligand in VCl₂(N‐2,6‐Me₂C₆H₃)(OAr) [OAr=O‐2,6‐Me₂C₆H₃ ( 1 ), O‐2,6‐i‐Pr₂C₆H₃ ( 2 ), O‐2,6‐Ph₂C₆H₃ ( 3 )].     

Novel Ni and Pd(benzocyclohexan‐ketonaphthylimino)2 complexes for copolymerization of norbornene with octene

Two novel late transition metals complexes with bidentate O?N chelate ligand, Mt(benzocyclohexan‐ketonaphthylimino)₂ {Mt(bchkni)₂: bchkni ?C₁₀H₈(O)C[N(naphthyl)CH₃]; Mt ? Ni, Pd}, were synthesized. In the presence of B(C₆F₅)₃, both complexes exhibited high activity toward the homo‐polymerization of norbornene (NB) (as high as 2.7 × 10⁵ g_polymer/mol_Ni·h for Ni(bchkni)₂/B(C₆F₅)₃ and 2.3 × 10⁵ g_polymer/mol_Pd·h for Pd(bchkni)₂/B(C₆F₅)₃, respectively). Additionally, both catalytic systems showed high activity toward the copolymerization of NB with 1‐octene under various polymerization conditions and produced the addition‐type copolymer with relatively high molecular weights (0.1–1.4 × 10⁵g/mol) as well as narrow molecular weight distribution. The 1‐octene content in the copolymers can be controlled up to 8.9–14.0% for Ni(bchkni)₂/B(C₆F₅)₃ and 8.8–14.6% for Pd(bchkni)₂/B(C₆F₅)₃ catalytic system by varying comonomer feed ratios from 10 to 70 mol %. The reactivity ratios of two monomers were determined to be r_1‐octene = 0.052, r_NB = 8.45 for Ni(bchkni)/B(C₆F₅)₃ system, and r_1‐octene = 0.025, r_NB = 7.17 for Pd(bchkni)/B(C₆F₅)₃ system by the Kelen‐TÜdÕs method. The achieved NB/1‐octene copolymers were confirmed to be noncrystalline and exhibited good thermal stability (T_d > 400°C, T_g = 244.1–272.2°C) and showed good solubility in common organic solvents. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Nickel(II) complexes bearing the bis(β‐ketoamino) ligand for the copolymerization of norbornene with a higher 1‐alkene

A novel bis(β‐ketoamino)Ni(II) complex catalyst, Ni{CF₃C(O)CHC[N(naphthyl)]CH₃}₂, was synthesized, and the structure was solved by a single‐crystal X‐ray refraction technique. The copolymerization of norbornene with higher 1‐alkene was carried out in toluene with catalytic systems based on nickel(II) complexes, Ni{RC(O)CHC[N(naphthyl)]CH₃}₂(R?CH₃, CF₃) and B(C₆F₅)₃, and high activity was exhibited by both catalytic systems. The effects of the catalyst structure and comonomer feed content on the polymerization activity and the incorporation rates were investigated. The reactivity ratios were determined to be r_1‐octene = 0.009 and r_norbornene = 13.461 by the Kelen–Tüdõs method for the Ni{CH₃C(O)CHC[N(naphthyl)]CH₃}₂/B(C₆F₅)₃ system. The achieved copolymers were confirmed to be vinyl‐addition copolymers through the analysis of ¹H‐NMR and ¹³C‐NMR. The thermogravimetric analysis results showed that the copolymers exhibited good thermal stability (decomposition temperature, T_dec > 400°C), and the glass‐transition temperature of the copolymers were observed between 215 and 275°C. The copolymers were confirmed to be noncrystalline by wide‐angle X‐ray diffraction analysis and showed good solubility in common organic solvents. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Ethylene/1‐octadecene copolymerization using [η5:η1‐C5Me4‐4‐R1‐6‐R‐C6H2O]TiCl2 catalysts

Copolymerization of ethylene with 1‐octadecene was studied using [η⁵:η¹‐C₅Me₄‐4‐R₁‐6‐R‐C₆H₂O]TiCl₂ [R₁ = ^tBu (1), H (2, 3, 4); R = ^tBu (1, 2), Me (3), Ph (4)] as catalysts in the presence of Al(i‐Bu)₃ and [Ph₃C][B(C₆F₅)₄]. The effect of the concentration of comonomer in the feed and Al/Ti molar ratio on the catalytic activity and molecular weight of the resultant copolymer were investigated. The substituents on the phenyl ring of the ligand affect considerably both the catalytic activity and comonomer incorporation. The 1 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system exhibits the highest catalytic activity and produces copolymers with the highest molecular weight, while the 2 /Al(i‐Bu)₃/[Ph₃C][B(C₆F₅)₄] catalyst system gives copolymers with the highest comonomer incorporation under similar conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Triazidotrinitro Benzene: 1,3,5‐(N3)3‐2,4,6‐(NO2)3C6

Triazidotrinitro benzene, 1,3,5‐(N₃)₃‐2,4,6‐(NO₂)₃C₆ ( 1 ) was synthesized by nitration of triazidodinitro benzene, 1,3,5‐(N₃)₃‐2,4‐(NO₂)₂C₆H with either a mixture of fuming nitric and concentrated sulfuric acid (HNO₃/H₂SO₄) or with N₂O₅. Crystals were obtained by the slow evaporation of an acetone/acetic acid mixture at room temperature over a period of 2 weeks and characterized by single crystal X‐ray diffraction: monoclinic, P 2₁/c (no. 14), a=0.54256(4), b=1.8552(1), c=1.2129(1) nm, β=94.91(1)°, V=1.2163(2) nm³, Z=4, ϱ=1.836 g⋅cm⁻³, R_all =0.069. Triazidotrinitro benzene has a remarkably high density (1.84 g⋅cm⁻³). The standard heat of formation of compound 1 was computed at B3LYP/6‐31G(d, p) level of theory to be ΔH°_f=765.8 kJ⋅mol⁻¹ which translates to 2278.0 kJ⋅kg⁻¹. The expected detonation properties of compound 1 were calculated using the semi‐empirical equations suggested by Kamlet and Jacobs: detonation pressure, P=18.4 GPa and detonation velocity, D=8100 m⋅s⁻¹.     

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.     

Ethylene/α‐olefin copolymerization by nonbridged (cyclopentadienyl)(aryloxy)titanium(IV) dichloride/AliBu3/Ph3CB(C6F5)4 catalyst systems

A series of nonbridged (cyclopentadienyl) (aryloxy)titanium(IV) complexes of the type, (η⁵‐Cp′)(OAr)TiCl₂ [OAr = O‐2,4,6‐^tBu₃C₆H₂ and Cp′ = Me₅C₅ ( 1 ), Me₄PhC₅ ( 2 ), and 1,2‐Ph₂‐4‐MeC₅H₂ ( 3 )], were prepared and used for the copolymerization of ethylene with α‐olefins (e.g., 1‐hexene, 1‐octene, and 1‐octadecene) in presence of AlⁱBu₃ and Ph₃CB(C₆F₅)₄ (TIBA/B). The effect of the catalyst structure, comonomer, and reaction conditions on the catalytic activity, comonomer incorporation, and molecular weight of the produced copolymers was examined. The substituents on the cyclopentadienyl group of the ligand in 1 – 3 play an important role in the catalytic activity and comonomer incorporation. The 1 /TIBA/B catalyst system exhibits the highest catalytic activity, while the 3 /TIBA/B catalyst system yields copolymers with the highest comonomer incorporation under the same conditions. The reactivity ratio product values are smaller than those by ordinary metallocene type, which indicates that the copolymerization of ethylene with 1‐hexene, 1‐octene, and 1‐octadecene by the 1–3/ TIBA/B catalyst systems does not proceed in a random manner. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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     

Highly Stereoselective Synthesis of Arylene‐Silylene‐Vinylene Polymers

Stereoregular trans‐arylene‐silylene‐vinylene polymers of M_w=13100–34800 and PDI=1.6–2.9 of the general formulas CH₂CH [ SiMe₂C₆H₄‐SiMe₂CHCH ] ( 16, 17, 18 ) and CH₂CH [ (R)CHCHC₆H₄CHCH ] (where R= Me₂Si‐p C₆H₄‐ SiMe₂ ,  Me₂Si‐m C₆H₄SiMe₂ and  Me₂SiC₆H₄C₆H₄SiMe₂ ) ( 19, 20, 21 ) have been effectively synthesized via silylative coupling (SC) homopolycondensation of bis(vinyldimethylsilyl)arenes ( 10, 12, 14 ) and cross‐polycondensation of 4‐(vinyldimethylsilyl)styrene ( 11 ) as well as cross‐copolycondensation of bis(vinyldimethylsilyl)arenes ( 10, 12 and 14 ) with 1,4‐divinylbenzene ( 9 ) catalyzed by [RuH(Cl)(CO)(PCy₃)₂] ( 7 ). Such highly stereoregular products cannot be synthesized via ADMET polycondensation or ring opening metathesis ROM or polyaddition of hydridosilanes to acetylenes.     

Efficient Access to Conjugated Dienones and Diene‐diones from Propargylic Alcohols and Enolizable Ketones: A Tandem Isomerization/Condensation Process Catalyzed by the Sixteen‐Electron Allyl‐Ruthenium(II) Complex [Ru(η3‐2‐C3H4Me)(CO)(dppf)] [SbF6]

A large variety of conjugated dienones R¹R²CCHCHC(R³)C(O)R⁴ and diene‐diones R¹R²CCHCHC{C(O)R³}C(O)R⁴ have been synthesized in high yields by reacting terminal propargylic alcohols HCCCR¹R²(OH) with enolizable ketones R³CH₂C(O)R⁴ and β‐dicarbonyl compounds R³C(O)CH₂C(O)R⁴, respectively. The process, which is catalyzed by the 16e^‐ (η³‐allyl)‐ruthenium(II ) complex [Ru(η³‐2‐C₃H₄Me)(CO)(dppf)] [SbF₆] associated with CF₃CO₂H, involves the initial isomerization of the propargylic alcohol into the corresponding α,β‐unsaturated aldehyde R¹R²CCHCHO (Meyer–Schuster rearrangement) and subsequent aldol‐type condensation.     

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 .     

Ring‐opening metathesis polymerization of norbornene catalyzed by tantalum and niobium complexes with chelating O‐donor ligands

BACKGROUND: In comparison with group 6 transition metals, such as tungsten and molybdenum, and group 8 metal ruthenium, group 5 metal‐based catalysts for ring‐opening metathesis polymerization (ROMP) have remained much less studied. The few reported ROMP catalysts of group 5 metals require multiple reaction steps to be synthesized, and are highly sensitive to air and moisture. RESULTS: A series of pentavalent tantalum and niobium complexes having catecholato, tropolonato, hinokitiolato, biphenolato and binaphtholato ligands were prepared and their catalytic activities for the ROMP of norbornene (NBE) were studied in the presence of trialkylaluminium as a co‐catalyst. Among these complexes, the tantalum complexes showed high activity upon activation with Buⁱ₃Al. In sharp contrast, the niobium complexes were effectively activated with Me₃Al. The polymers obtained with these complexes had high molecular weights (M_n > 10⁵ g mol⁻¹) and relatively narrow molecular weight distributions (M_w/M_n ≈ 2). CONCLUSION: We found that easily accessible and relatively stable tantalum and niobium complexes with such chelating O‐donor ligands showed high catalytic activity for ROMP of NBE depending on the kind of co‐catalyst. These findings could contribute to future development of ROMP catalysts. Copyright © 2008 Society of Chemical Industry     

Nickel(II) Chloride‐Catalyzed Regioselective Hydrothiolation of Alkynes

Regioselective Markovnikov‐type addition of PhSH to alkynes (HC≡C‐R) has been performed using easily available nickel complexes. The non‐catalytic side reaction leading to anti‐Markovnikov products was suppressed by addition of γ‐terpinene to the catalytic system. The other side reaction leading to the bis(phenylthio)alkene was avoided by excluding phosphine and phosphite ligands from the catalytic system. It was found that catalytic amounts of Et₃N significantly increased the yield and selectivity of the catalytic reaction. Under optimized conditions high product yields of 60–85% were obtained for various alkynes [R=n‐C₅H₁₁, CH₂NMe₂, CH₂OMe, CH₂SPh, C₆H₁₁(OH), (CH₂)₃CN]. The X‐ray structure of one of the synthesized products is reported.     

Novel and Mild Route to Phthalocyanines and 3‐Iminoisoindolin‐1‐ones via N,N‐Diethylhydroxylamine‐Promoted Conversion of Phthalonitriles and a Dramatic Solvent‐Dependence of the Reaction

Refluxing a mixture of phthalonitrile C₆R¹R²R³R⁴(CN)₂ 1 (R¹–R⁴=H), or its substituted derivatives 2 (R¹, R³, R⁴=H, R²=Me), or 3 (R¹, R⁴=H, R², R³=Cl) (1 equiv.) and N,N‐diethylhydroxylamine, Et₂NOH, (4 equivs.) in methanol for 4 h results ( Route A ) in precipitation of the symmetrical ( 6 and 8 ) and an isomeric mixture of unsymmetrical ( 7 ) phthalocyanines, isolated in good (55–65 %) yields. The reaction of phthalonitriles 1 , 2 , or 4 (R¹, R³, R⁴=H, R²=NO₂) (4 equivs.) with Et₂NOH (8 equivs.) in the presence of a metal salt MCl₂ (M=Zn, Cd, Co, Ni) (1 equiv.) in n‐BuOH or without solvent results in the formation of metallated phthalocyanine species ( 9 – 17 ). Upon refluxing in freshly distilled dry chloroform, phthalonitrile 1 or its substituted analogues 2 , 3 or 5 (R¹–R⁴=F) (1 equiv.) react with N,N‐diethylhydroxylamine (2 equivs.) affording 3‐iminoisoindolin‐1‐ones 18 – 21 ( Route B ) isolated in good yields (55–80 %). All the prepared compounds were characterized with C, H, and N elemental analyses, ESI‐MS, IR, and compounds 18 – 21 also by 1D (¹H, ¹³C{¹H}), and 2D (¹H,¹⁵N‐HMBC and ¹H,¹³C‐HMQC, ¹H,¹³C‐HMBC) NMR spectroscopy.     

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.     

Mechanistic in situ High‐Pressure NMR Studies of Benzene Hydrogenation by Supramolecular Cluster Catalysis with [(η6‐C6H6)(η6‐C6Me6)2Ru3(μ3‐O)(μ2‐OH)(μ2‐H)2][BF4]

In situ high‐pressure NMR spectroscopy of the hydrogenation of benzene to give cyclohexane, catalysed by the cluster cation [(η⁶‐C₆H₆) (η⁶‐C₆Me₆)₂Ru₃(μ₃‐O)(μ₂‐OH)(μ₂‐H)₂]⁺ 2 , supports a mechanism involving a supramolecular host‐guest complex of the substrate molecule in the hydrophobic pocket of the intact cluster molecule.     

Propylene polymerization with rac‐(EBl)Zr(NC4H8)2 cocatalyzed by MAO or AlR3 and anionic compounds

Propylene polymerization was carried out using an ansa‐zirconocene pyrrolidide based catalytic system of racemic ethylene‐1,2‐bis(1‐indenyl)zirconium dipyrrolidide [rac‐(EBI)Zr(NC₄H₈)₂ or (rac‐1)] and methylaluminoxane (MAO) or a noncoordinating anion. In situ generation of cationic alkylzirconium species was also investigated by NMR‐scale reactions of rac‐1 and MAO, and rac‐1, AlMe₃, and [Ph₃C] [B(C₆F₅)₄]. In the NMR‐scale reaction using CD₂Cl₂ as a solvent, a small amount of MAO ([Al]/[Zr] = 30) was enough to completely activate rac‐1 to give cationic methylzirconium cations that can polymerize propylene. The resulting isotactic polypropylene (iPP) isolated in this reaction showed a meso pentad value of 91.3%. In a similar NMR‐scale reaction rac‐1 was stoichiometrically methylated by AlMe₃ to give rac‐(EBI)ZrMe₂, and the introduction of [Ph₃C] [B(C₆F₅)₄] into the reaction mixture containing rac‐(EBI)ZrMe₂ led to in situ generation of cationic [rac‐(EBI)Zr(μ‐Me)₂AlMe₂]⁺ species that can polymerize propylene to give iPP showing a meso pentad value of 94.7%. The catalyst system rac‐1/MAO exhibited an increase of activity as the [Al]/[Zr] ratio increased within an experimental range ([Al]/[Zr] = 930–6511). The meso pentad values of the resulting iPPs were in the range of 83.2–87.5%. The catalytic activity showed a maximum (R _p = 6.66 × 10⁶ g PP/mol Zr h atm) when [Zr] was 84.9 × 10⁻⁶ mol/L in the propylene polymerization according to the concentration of catalyst. MAO‐free polymerization of propylene was performed by a rac‐1/AlR₃/noncoordinating anion catalytic system. The efficiency of AlR₃ was decreased in the order of AlMe₃ (R _p = 13.0 × 10⁶ g PP/mol Zr h atm) > Al(i‐Bu)₃ (8.9 × 10⁶) > AlPr₃ (8.8 × 10⁶) > Al(i‐Bu)₂H (8.4 × 10⁶) > AlEt₃ (8.4 × 10⁶). The performance of the noncoordinating anion as a cocatalyst was on the order of [HNMePh₂][B(C₆F₅)₄] (R _p = 13.0 × 10⁶ g PP/mol Zr h atm) > [HNMe₂Ph][B(C₆F₅)₄] (10.8 × 10⁶) > [Ph₃C][B(C₆F₅)₄] (8.4 × 10⁶) > [HNEt₂Ph][B(C₆F₅)₄] (7.8 × 10⁶). The properties of iPP were characterized by ¹³C‐NMR, FTIR, DSC, GPC, and viscometry. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 875–885, 1999     

Copolymerization of butadiene with styrene using a rare‐earth metal compound – dialkylmagnesium – halohydrocarbon catalytic system

Copolymerizations of butadiene (Bd) with styrene (St) were carried out with catalytic systems composed of a rare‐earth compound, Mg(n‐Bu)₂ (di‐n‐butyl magnesium) and halohydrocarbon. Of all the rare earth catalysts examined, Nd(P₅₀₇)₃–Mg(n‐Bu)₂–CHCl₃ showed a high activity in the copolymerization under certain conditions: [Bd] = [St] = 1.8 mol l^?1, [Nd] = 6.0 × 10^?3 mol l^?1, Mg/Nd = 10, Cl/Nd = 10 (molar ratio), ageing for 2 h, copolymerization at 50 °C for 6–20 h. The copolymer of butadiene and styrene obtained has a relatively high styrene content (10–30 mol%), cis‐1,4 content in butadiene unit (85–90%), and molecular weight ([η] = 0.8–1 dL g^?1). Monomer reactivity ratios were estimated to be r_Bd = 36 and r_St = 0.36 in the copolymerization. © 2002 Society of Chemical Industry     

Reduction electrochimique a l'electrode de mercure de composes α-hydroxycarbonyles en solution aqueuse α — I. Glyoxals RCOCH(OH)2

Reduction at the mercury electrode in aqueous solution of the unhydrated form of glyoxals exhibits evidence of a reversible system: RCOCHO + 2e + 2H⁺ ?har2; RC(OH)CHOH with RCH₃ or C₆H₅.For the hydrated form C₆H₅COCH(OH)₂, investigation indicated occurrence of two types of irreversible processes. In neutral media transfer of two electrons involve either the hydrogenolysis of the COH bond, yielding hydroxyacétophenone: C₆H₅COCH₂OH, or alternatively the reduction of the keto grouping yielding mandelaldehyde: C₆H₅CHOHCHO.The COH cleavage is exclusive in acidic media and for aliphatic glyoxals RCOCH(OH)₂.