Transition metal complexes bearing 2,6-bis(imino)pyridyl: Synthesis,structure, ethylene polymerization/ oligomerization studies

A series of new complexes {2,6-bis[1-((2-methyl-4-methoxyphenyl)imino)ethyl]pyridine}Cl₂ [M=Fe(II) (2), Co(II) (3), Ni(II) (4), Cu(II) (5), Zn(II) (6)] have been synthesized. At 25°C, using 500 equiv of methylaluminoxane (MAO), the activities of Fe(II), Co(II) catalysts can reach 4.02 ×10⁶ g/mol-Fehatm for ethylene polymerization and 3.98×10⁵ g/mol-Cohatm for ethylene oligomerization. The effects of polymerization conditions such as reaction temperature, Al/M molar ratio and time on the activity of catalyst have been explored.

     

Pre-column chelation liquid chromatographic separation and determination of trace V,Cu, Co,Pd, Fe and Ni

Conditions for the separation by reversed-phase liquid chromatography (LC) of V(V), Cu(II), Co(III), Pd(II), Fe(III) and Ni(II) chelates with 2-(5-bromopyridylazo)-5-diethylaminophenol (5-Br-PADAP) were studied. Six species of metal chelates were separated successfully with methanol-acetonitrile-water (72:12:16, v/v/v) containing 0.13 M NaCl and 0.29 mM cetyltrimethylammonium bromide (pH 5.0) as the mobile phase on a Nucleosil C₁₈ (5 μm) column (250 × 4 mm i.d.).The conditions of the determination of these metal chelates are discussed. A simple and rapid method for the determination of trace amounts of V(V), Cu(II), Co(III), Pd(II) and Ni(II) simultaneously by reversed-phase LC has been developed. The detection limits are 5 × 10^?12, 1 × 10^?10, 3 × 10^?11, 5.3 × 10^?9 and 2 × 10^?10 g, respectively. The method is applied to the determination of these metals in natural waters and mineral samples.     

Cycloheptyl‐fused NNO‐ligands as electronically modifiable supports for M(II) (M = Co,Fe) chloride precatalysts; probing performance in ethylene oligo‐/polymerization

The N,N,O‐cobalt(II), [2,3‐{C₄H₈C(NAr)}:5,6‐{C₄H₈C(O)}C₅HN]CoCl₂ (Ar = 2,6‐(CHPh₂)₂‐4‐MeC₆H₂ Co1 , 2,6‐(CHPh₂)₂‐4‐EtC₆H₂ Co2 , 2,6‐(CHPh₂)₂‐4‐ClC₆H₂ Co3 , 2,6‐(CHPh₂)₂‐4‐FC₆H₂ Co4 ) and N,N,O‐iron(II) complexes, [2,3‐{C₄H₈C(NAr)}:5,6‐{C₄H₈C(O)}C₅HN]FeCl₂ (Ar = 2,6‐(CHPh₂)₂‐4‐MeC₆H₂ Fe1 , 2,6‐(CHPh₂)₂‐4‐EtC₆H₂ Fe2 , 2,6‐(CHPh₂)₂‐4‐ClC₆H₂ Fe3 , 2,6‐(CHPh₂)₂‐4‐FC₆H₂ Fe4 ), each containing one sterically enhanced but electronically modifiable N‐2,6‐dibenzhydryl‐4‐R²‐phenyl group, have been prepared by a one‐pot template approach using α,α′‐dioxo‐2,3:5,6‐bis(pentamethylene)pyridine, the corresponding aniline along with the respective cobalt or iron salt in acetic acid. Distorted square pyramidal geometries are a feature of the molecular structures of Co1 – Co4 . Upon activation with MAO or MMAO, Co1 – Co4 show good activities (up to 2.2 × 10⁵ g mol^?1(Co) h^?1) affording short chain oligomers (C₄–C₃₀) with good α‐olefin selectivity. By contrast, Fe1 – Fe4 , in the presence of MMAO, displayed moderate activities (up 10.9 × 10⁴ g(PE) mol^?1(Fe) h^?1) for ethylene polymerization forming low‐molecular‐weight linear polymers (up to 13.0 kg mol^?1) incorporating saturated n‐propyl and i‐butyl chain ends. For both cobalt and iron, the precatalysts incorporating the more electron withdrawing 4‐R²‐substituents [Cl ( Co3 / Fe3 ), F ( Co4 / Fe4 )] deliver the best catalytic activities, while with cobalt, these types of substituents additionally broaden the oligomeric distribution. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3980–3989     

Photometric determination of aqueous cobalt (II), nickel (II), copper (II) and iron (III) with 1-nitroso-2-naphthol-3,6-disulfonic acid disodium salt in gelatin films

Photometric determination of aqueous Co(II), Cu(II), Ni(II) and Fe(III) was performed using indicator films prepared by immobilization of 1-nitroso-2-naphthol-3,6-disulfonic acid disodium salt (NRS) into hardened photographic film. Immobilization was based on electrostatic interaction of reagent and metal complexes with the gelatin. The isoelectric point pH of hardened gelatin (4.46±0.04) was evaluated by viscometry. Co(II), Fe(III), Ni(II) form 1:3 complexes with NRS in gelatin at pH 2 and Cu(II) forms 1:2 complexes. Their log β′ values were: Co-6.7, Fe-8.6, Cu-8.0, and Ni-6.4. The absorption maxima were: 370nm for NRS, and 430nm, 470nm, 495nm and 720nm for complexes of Co(II), Ni(II), Cu(II) and Fe(III). An algorithm for their simultaneous determination using the indicator films was developed. The detection limits were: c_lim(Co²⁺) = 0.45×10⁻⁵ M, c_lim(Fe³⁺) = 0.50×10⁻⁵ M, c_lim(Cu²⁺) = 0.67×10⁻⁵ M, c_lim(Ni²⁺) = 0.75×10⁻⁵ M,; and their sum c_lim(ΣMn⁺) = 0.82×10⁻⁵ M.      

Novel cyclohexyl‐substituted salicylaldiminato–nickel(II) complex as a catalyst for ethylene homopolymerization and copolymerization

The cyclohexyl‐substituted salicylaldiminato–Ni(II) complex [O? (3‐C₆H₁₁)(5‐CH₃)C₆H₂CH?N‐2,6‐C₆H₃ⁱPr₂]Ni(PPh₃)(Ph) ( 4 ) has been synthesized and characterized with ¹H NMR and X‐ray structure analysis. In the presence of phosphine scavengers such as bis(1,5‐cyclooctadiene)nickel(0) [Ni(COD)₂], triisobutylaluminum (TIBA), and triethylaluminum (TEA), 4 is an active catalyst for ethylene polymerization and copolymerization with the polar monomers tert‐butyl‐10‐undecenoate, methyl‐10‐undecenoate, and 4‐penten‐1‐ol under mild conditions. The polymerization parameters affecting the catalytic activity and viscosity‐average molecular weight of polyethylene, such as the temperature, time, ethylene pressure, and catalyst concentration, are discussed. A polymerization activity of 3.62 × 10⁵ g of PE (mol of Ni h)^?1 and a weight‐average molecular weight of polyethylene of 5.73 × 10⁴ g^.mol^?1 have been found for 10 μmol of 4 and a Ni(COD)₂/ 4 ratio of 3 in a 30‐mL toluene solution at 45 °C and 12 × 10⁵ Pa of ethylene for 20 min. The polydispersity index of the resulting polyethylene is about 2.04. After the addition of tetrahydrofuran and Et₂O to the reaction system, 4 exhibits still high activity for ethylene polymerization. Methyl‐10‐undecenoate (0.65 mol %), 0.74 mol % tert‐butyl‐10‐undecenoate, and 0.98 mol % 4‐penten‐1‐ol have been incorporated into the polymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6071–6080, 2004     

Flotation Separation of Lead with Sodium Nitrate‐Potassium Iodide‐Cetyltrimethyl Ammonium Bromide System

The flotation separation behavior of lead with Sodium Nitrate‐Potassium Iodide‐Cetyltrimethyl Ammonium Bromide system and the conditions for the separation of lead with other metal ions are studied in this research. With 0.1 M potassium iodide, 1.0 × 10^?2 M Cetyltrimethyl Ammonium Bromide and 1.0 g/10 mL of sodium nitrate, Pb(II) can form an ion‐association complex (PbI₄^2?) (CTMAB⁺)₂ and be separated completely from Zn(II), Fe(III), Co(II), Ni(II), Mn(II) and Al(III) by flotation at pH = 1.0–3.0.     

Catalytic Adsorptive Stripping Chronopotentiometry of Co(II)‐DMG‐Bromate System at an In Situ Plated Lead Film Electrode

A novel catalytic adsorptive stripping chronopotentiometric (CC‐CAdSCP) procedure for the determination of Co(II) traces was developed using a lead film electrode (PbFE). The PbFE was generated in situ on a glassy carbon support from a 0.1 M ammonia buffer containing 1×10^?5 M Pb(II), 6.5×10^?5 M DMG and the target metals. An addition of 0.2 M NaBrO₃ to the solution yielded an 11‐fold catalytic enhancement of chronopotentiometric response of the Co(II)‐DMG complex. The CC‐CAdSCP curves were well‐developed, sharp and reproducible (RSD 5.0 % for 5×10^?9 M Co(II)). The limit of detection for Co(II) for 210 s of accumulation time was 4×10^?10 M (0.024 µg L^?1). In addition, the elaborated method allowed the simultaneous quantification of Co(II) and Ni(II) simultaneously.     

Controlled isoprene polymerization mediated by iminopyridine‐iron (II) acetylacetonate pre‐catalysts

A ligand controlled stereoselective polymerization of isoprene has been developed. A series of (aryl/alkyl)‐iminopyridine iron (II) acetylacetonate complexes: (aryl = Ph Fe1 ; alkyl = CH₂Ph Fe2 , CH (Ph)₂ Fe3 , CH (Me)₂ Fe4 , C (Me)₃ Fe5 , C (Me)₂CH₂C(Me)₃ Fe6 ), has been prepared in which steric and electronic substituents systematically modified to investigate their influences for isoprene polymerization. The molecular structure of representative complex Fe2 was confirmed by single crystal X‐ray diffraction and, revealed a distorted octahedral geometry at iron center. On treatment with methylaluminoxane (MAO), Fe1 – Fe6 displayed low ( Fe5 & Fe6 ) to high activities ( Fe1 – Fe4 ) with quantitative monomer conversion (>99%) for isoprene polymerization producing polyisoprene of high molecular weight (up to 2.0 × 10⁵ g/mol) and unimodal molecular weight distribution (1.4–3.3). Specifically, complex Fe2 (alkyl = CH₂Ph) displayed the highest activity of 7.0 × 10⁶ g (mol of Fe)^?1 h^?1 with 85% conversion of monomer over run time of 10 min at 25 °C. While, Fe6 catalyzed polyisoprene possessed high content of trans‐1,4 unit (up to 87%). Furthermore, the influence of the reaction parameters and the nature of the ligands on the catalytic activities and microstructural properties of the polymer were investigated in detail.     

Kinetic Study of the Reduction of Bromate Ion by Tris(1,10-Phenanthroline)Iron(II) and Aquoiron(II) Ions — Implication for the Bromate-Gallic Acid Oscillating Reaction

The kinetics of the bromate oxidation of tris(1,10-phenanthroline)iron(II) (Fe(phen)₃²⁺) and aquoiron(II) (Fe²⁺ (aq)) have been studied in aqueous sulfuric acid solutions at μ = 1.0M and with Fe(II) complexes in great excess. The rate laws for both reactions generally can be described as -d [Fe(II)]/6dt = d[Br^?]/dt = k[Fe(II)] [BrO^?₃] for [H⁺]₀ = 0.428–1.00M. For [BrO^?₃]₀ = 1.00 × 10^?4M. [Fe²⁺]₀ = (0.724–1.45)x 10^?2 M, and [H⁺]₀ = 1.00M, k = 3.34 ± 0.37 M^?1s^?1 at 25°. For [BrO^?₃]₀ = (1.00–1.50) × 10^?4M, [Fe²⁺]₀ = 7.24 × 10^?3M ([phen]₀ = 0.0353M), and [H⁺]₀ = 1.00M, k = (4.40 ± 0.16) × 10^?2 M^?1s^?1 at 25°. Kinetic results suggest that the BrO^?₃-Fe²⁺ reaction proceeds by an inner-sphere mechanism while the BrO^?₃-Fe(phen)₃²⁺ reaction by a dissociative mechanism. The implication of these results for the bromate-gallic acid and other bromate oscillators is also presented.     

Ethylene Oligomerization Catalyzed by MCl2(PPh3)2 Complex‐es/Ethylaluminoxane

The catalytic properties of MCl₂ (PPh₃)₂ (M = Fe, A; Co, B; Ni, C) in combination with ethylaluminoxane (EAO) as cocatalyst for ethylene oligomerization have been investigated. Treatment of the MCl₂ (PPh₃)₂ complexes with EAO in toluene generated active catalysts in situ that are capable of oligomerizating ethylene to low‐carbon olefins. The catalytic activity and product distribution were affected by reaction condition, such as reaction temperature, the ratios of Al/M and the reaction time. The activity of 1.70 × 10⁵ g oligomers/ (mol Co. h) for the catalytic system of CoCl₂(PPh₃)₂ with EAO at 200°C was observed, with the selectivity of 91.1% to C_4–10 olefins and 70.7% to C_4–10 linear α‐olefins.     

A novel spectrophotometric method for determination of cyanide using cobalt (II) phthalocyanine tetracarboxylate as a chromogen

Cobalt (II) phthalocyanine tetracarboxylate [Co (II)Pc-COOH] has been prepared and used in aqueous solutions as a novel chromogenic reagent for the spectrophotometric determination of cyanide ion. The method is based on measuring the increase in the intensity of the monomer peak in the reagent absorbance at 682 nm due to the formation of a 1 : 2 [Co (II)Pc-COOH] : [CN] complex. The complex exhibits a molar absorptivity (ε) of 7.7 × 10⁴ L mol^?1 cm^?1 and a formation constant (K_f ) of 5.4 ± 0.01 × 10⁶ at 25 ± 0.1°C. Beer's law is obeyed over the concentration range 0.15–15 µg mL^?1 (5.8 × 10^?6–5.8 × 10^?4 M) of cyanide ion, the detection limit is 20 ng mL^?1 (7.7 × 10^?7 M) the relative standard deviation is ±0.7% (n = 6) and the method accuracy is 98.6 ± 0.9%. Interference by most common ions is negligible, except that by sulphite. The proposed method is used for determining cyanide concentration in gold, silver and chromium electroplating wastewater bath solutions after a prior distillation with 1 : 1 H₂SO₄ and collection of the volatile cyanide in 1 M NaOH solution containing lead carbonate as recommended by ASTM, USEPA, ISO and APAHE separation procedures. The results agree fairly well with potentiometric data obtained using the solid state cyanide ion selective electrode.     

Heptane-soluble homogeneous zirconocene catalyst: Synthesis of a single diastereomer,polymerization catalysis,and effect of silica supports

Bis(1-indenyl)-di[1′S, 2′R, 5′S)-methoxy]silane ( 1 ) was converted into a mixture of corresponding ansa-diastereomeric zirconocenes. Further purification afforded a single dia-stereomer, di[(1′S, 2′R, 5′S)-methoxy] silylene-bis[η⁵-1(R, R)-(+)-indenyl] dichlorozirconium ( 2 ), which is optically active and hydrocarbon soluble. Extremely rapid ethylene, propylene, and ethylene-hexene polymerizations were observed both in toluene and n-heptane solutions; for instance, at 50°C, activity for ethylene polymerization reaches ～ 1.5×10¹⁰ (g of PE/((mol of Zr) · [C₂H₄] · h). The “bare” zirconocenium ion generated from 2/TIBA/Ph₃CB(C₆F₅)₄ exhibits unusual polymerization behaviors; the polymerization activity increases monotonically with temperature of polymerization (T_p) up to a conventional polymerization condition (50–70°C), and the ¹³C NMR study shows that the isotactic poly-propylene obtained has fairly high [mmmm] methyl pentad distributions at high T_p (?25°C with [mmmm] ～ 0.93–0.75) and a perfect stereoregularity at low T_p (?0°C with [mmmm] > 0.99). The catalyst precursors 2 and Et(Ind)₂ZrCl₂ ( 3 ) supported on silica by different approaches produced poly(olefins) of different molecular weights and stereoregularities, and a methylaluminokane and Ph₃CB(C₆F₅)₄ free silica-supported zirconocene system was found to be activated by triisobutylaluminum. © 1995 John Wiley & Sons, Inc.     

Exceptionally high molecular weight linear polyethylene by using N,N,N′‐Co catalysts appended with a N′‐2,6‐bis{di(4‐fluorophenyl)methyl}‐4‐nitrophenyl group

The bis(arylimino)pyridines, 2‐[CMeN{2,6‐{(4‐FC₆H₄)₂CH}₂–4‐NO₂}]‐6‐(CMeNAr)C₅H₃N (Ar = 2,6‐Me₂C₆H₃ L1 , 2,6‐Et₂C₆H₃ L2 , 2,6‐i‐Pr₂C₆H₃ L3 , 2,4,6‐Me₃C₆H₂ L4 , 2,6‐Et₂–4‐MeC₆H₂ L5 ), each containing one N′‐2,6‐bis{di(4‐fluorophenyl)methyl}‐4‐nitrophenyl group, have been synthesized by two successive condensation reactions from 2,6‐diacetylpyridine. Their subsequent treatment with anhydrous cobalt (II) chloride gave the corresponding N,N,N′‐CoCl₂ chelates, Co1 – Co5 , in excellent yield. All five complexes have been characterized by ¹H/¹⁹F NMR and IR spectroscopy as well as by elemental analysis. In addition, the molecular structures of Co1 and Co3 have been determined and help to emphasize the differences in steric properties imposed by the inequivalent N‐aryl groups; distorted square pyramidal geometries are adopted by each complex. Upon activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), precatalyts Co1 – Co5 collectively exhibited very high activities for ethylene polymerization with 2,6‐dimethyl‐substituted Co1 the most active (up to 1.1 × 10⁷ g (PE) mol^?1 (Co) h^?1); the MAO systems were generally more productive. Linear polyethylenes of exceptionally high molecular weight (M_w up to 1.3 × 10⁶ g mol^?1) were obtained in all cases with the range in dispersities exhibited using MAO as co‐catalyst noticeably narrower than with MMAO [M_w/M_n: 3.55–4.77 ( Co1 – Co5 /MAO) vs. 2.85–12.85 ( Co1 – Co5 /MMAO)]. Significantly, the molecular weights of the polymers generated using this class of cobalt catalyst are higher than any literature values reported to date using related N,N,N‐bis (arylimino)pyridine‐cobalt catalysts.     

Activity and stability spontaneously enhanced toward ethylene polymerization by employing 2‐(1‐(2,4‐dibenzhydrylnaphthylimino)ethyl)‐6‐(1‐(arylimino)ethyl) pyridyliron(II) dichlorides

A series of 2‐(1‐(2,4‐dibenzhydrylnaphthylimino)ethyl)‐6‐(1‐(arylimino)ethyl)pyridyliron(II) complexes ( Fe1 ? Fe5 ) was synthesized and characterized. The molecular structure of the representative Fe2 was determined by single‐crystal X‐ray diffraction, revealing a distorted pseudo‐square‐pyramidal geometry around the iron center. On activation with either methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all these iron complex precatalysts performed with high activities (up to 1.58 × 10⁷ g (PE) mol^?1 (Fe) h^?1) toward ethylene polymerization, producing highly linear polyethylenes with high molecular weight and bimodal distribution, which was in accordance with high temperature ¹³C NMR, high T _m values (T _m ～130 °C) and the GPC curves of the obtained polyethylenes. Meanwhile, DFT calculation results also showed the good correlation between net charges on iron and experimental activities. Compared with previous bis(imino)pyridyliron analogues, the current iron complexes containing the benzhydrylnaphthyl groups exhibited relatively higher activities and better thermal‐stability at elevated temperatures, especially at 80 °C as the industrial operating temperature, and still showed high activities toward ethylene polymerization up to 8.57 × 10⁶ g (PE) mol^?1 (Fe) h^?1 in the presence of co‐catalyst MMAO. In addition, these iron complex precatalysts all exhibited long lifetimes. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 988–996     

Synergistic solvent extraction of copper, cobalt, rhodium and iridium into 1, 2-Dichloroethane at trace level by newly synthesized 25, 26, 27, 28-tetrahydroxy-5, 11, 17, 23-tetra-[4-(N-hydroxyl-3-phenylprop-2-enimidamido) phenylazo] calix[4]arene

A spectrophotometric method for determination of copper, cobalt, rhodium and iridium ions from nitric acid media after extraction of these ions by 25, 26, 27, 28-tetrahydroxy-5, 11, 17, 23-tetra-[4-(N-hydroxyl-3-phenylprop-2-enimidamido) phenylazo] calix [4] arene (THPAC) has been developed and possible synergistic effect has been investigated. The maximum enhancement was obtained in the presence of 30% 1, 2-dichloroethane in DMF and 3M nitric acid. The trace amounts of the metal were determined spectrophotometrically. Beer’s law was obeyed in concentration range 5.0–10.0 μg, 6.0–120.0 μg, 12.0–100.0 μg, and 10.0–130.0 μg/10 mL of the final solution of copper, cobalt, rhodium and iridium, respectively. The molar absorptivities (l mol^?1 cm^?1) and Sandell’s sensitivities (μg cm^?1) were calculated: Cu (II) = 0.96 × 10^4, 0.0066; Co (II) = 1.13 × 10⁴, 0.0052; Rh (III) = 0.98 × 10⁴, 0.012; and Ir (III) = 2.03 × 10⁴, 0.0095, respectively. Seven replicate analyses containing of 20.0 μg of Cu (II), 24.0 μg of Co (II), 36.0 μg of Rh (III) and 25.0 μg of Ir (III) gave mean absorbance 0.302, 0.462, 0.344, 0.264; and relative standard deviation 0.65, 0.85, 1.10, 1.08%, respectively. The interference of various ions was studied and optimum conditions were developed for determination of metals in certain alloys, environmental, pharmaceutical and synthetic samples.     

Ethylene polymerization with long‐lifetime monopendant thienyl‐substituted group 4 metallocenes

A series of group 4 metallocenes (RCp)[Cp―(bridge)―(2‐C₄H₃S)]MCl₂ [M = Ti ( C1 , C2 , C3 , C4 ); M = Zr ( C5 , C6 , C7 , C8 )] bearing a pendant thiophene group on a cyclopentadienyl ring have been synthesized, characterized and tested as catalyst precursors for ethylene polymerization. The molecular structures of representative titanocenes C2 and C4 were confirmed by single‐crystal X‐ray diffraction and revealed that both complexes exist in an expected coordination environment for a monomeric bent metallocene. No intramolecular coordination between the thiophene group and the titanium center could be observed in the solid state. Upon activation by methylaluminoxane (MAO), titanocenes C1 , C2 , C3 , C4 showed moderate catalytic activities and produced high‐ or ultra‐high‐molecular‐weight polyethylene (M_v 70.5–227.1 × 10⁴ g mol^?1). Titanocene C3 is more active and long‐lived, with a lifetime of nearly 9 h at 30 °C. At elevated temperatures of 80–110 °C, zirconocenes C5 , C6 , C7 , C8 displayed high catalytic activities (up to 27.6 × 10⁵ g PE (mol Zr)^?1 h^?1), giving high‐molecular‐weight polyethylene (M_v 11.2–53.7 × 10⁴ g mol^?1). Even at 80 °C, a long lifetime of at least 2 h was observed for the C8/MAO catalyst system. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of para-Substituents in Ethylene Copolymerizations with 1-Decene, 1-Dodecene,and with 2-Methyl-1-Pentene Using Phenoxide Modified Half-Titanocenes-MAO Catalyst Systems

Effect of para-substituents in the ethylene (E) copolymerization with 1-decene (DC), 1-dodecene (DD), and with 2-methyl-1-pentene (2M1P) using a series of Cp*TiCl₂(O-2,6-ⁱPr₂-4-R-C₆H₂) [R=H ( 1 ), ^tBu ( 2 ), Ph ( 3 ), CHPh₂ ( 4 ), CPh₃ ( 5 ), SiMe₃ ( 6 ), SiEt₃ ( 7 ), and newly prepared 4-^tBuC₆H₄ ( 8 ) and 3,5-Me₂C₆H₃ ( 9 )]-MAO catalyst systems has been studied. The activities in these copolymerization reactions were affected by the para-substituent, and the SiMe₃ ( 6 ), SiEt₃ ( 7 ) and 3,5-Me₂C₆H₃ ( 9 ) analogues showed the higher activities at 50 °C in the E copolymerization reactions with DC (1.06–1.44×10⁶ kg-polymer/mol-Ti⋅h), DD (1.04–1.88×10⁶ kg-polymer/mol-Ti⋅h) than the others, whereas no significant differences were observed in the comonomer incorporations. Complexes 6 and 7 also showed the higher activities at 50 °C in the E/2M1P copolymerization, and the 2M1P incorporation was affected by the para-substituent and the polymerization temperature; complex 9 showed better 2M1P incorporation at 25 °C.     

Kinetic studies of the oxidation of transition metal(II) malate complexes by peroxomonosulphate

The kinetics of oxidation of malic acid by peroxomonosulphate (PMS) in the presence of Cu(II) (2.50 × 10^?4–5.00 × 10^?3 M), Co(II) (2.00 × 10^?6–1.00 × 10^?5 M) and Ni(II) (5.00 × 10^?4–6.00 × 10^?3 M) were studied in the pH range 4.05–5.89. The oxidation of Ni(II) malate follows simple first-order kinetics with respect to both [PMS] and [Ni(II)], while the oxidations of Cu(II) malate and Co(II) malate show autocatalysis. There is an appreciable induction period in the Cu(II) malate oxidation, while Co(II) malate oxidation follows a simple curve. The initial oxidation product for all three systems was identified as malonic semialdehyde. Alcohol quenching studies suggest that, even in the Co(II) malate-PMS system, no radical intermediates such as $ {\text{SO}}_{4}^{ - .} $ or $ {\text{OH}}{}^{.} $ are detected. The malonic semialdehyde intermediate may react with M(II) malates to give a hemiacetal, which may be more reactive.     

Thermo‐stable 2‐(arylimino)benzylidene‐9‐arylimino‐5,6,7,8‐tetrahydro cyclohepta[b]pyridyliron(II) precatalysts toward ethylene polymerization and highly linear polyethylenes

A series of 2‐(arylimino)benzylidene‐9‐arylimino‐5,6,7,8‐tetrahydrocyclohepta[b] pyridyliron(II) chlorides was synthesized and characterized using FT‐IR and elemental analysis, and the molecular structures of complexes Fe3 and Fe4 have been confirmed by the single‐crystal X‐ray diffraction as a pseudo‐square‐pyramidal or distorted trigonal‐bipyramidal geometry around the iron core. On activation with methylaluminoxane (MAO) or modified methylaluminoxane (MMAO), all iron precatalysts exhibited high activities toward ethylene polymerization with a marvelous thermo‐stability and long lifetime. The Fe4 /MAO system showed highest activity of 1.56 × 10⁷ gPE·mol^?1(Fe)·h^?1 at 70 °C, which is one of the highest activities toward ethylene polymerization by iron precatalysts. Even up to 80 °C, Fe3 /MAO system still persist high activity as 6.87 × 10⁶ g(PE)·mol^?1(Fe)·h^?1, demonstrating remarkable thermal stability for industrial polymerizations (80–100 °C). This was mainly attributing to the phenyl modification of the framework of the iron precatalysts. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 830–842     

Electron transfer reaction of electrochemically polymerized tris-(amino-phenanthroline)-iron(II/III) complex films

New films of iron complex with 4,7-bis(2-aminophenyl)-methylaminosulfonylphenyl)-1,10-phenanthroline (APP) and 5-amino-1,10-phenanthroline (AP) are prepared on the electrode surface of In–Sn oxide conducting glass (ITO) by electrochemical oxidation. The thickness (Φ) of the films prepared on the ITO can be controlled by the number of cycles of the potential scan. The resulting film-coated electrodes show well-defined reversible vol-tammograms corresponding to the redox reaction of the Fe(II/III) complexes in 0.1 M NaClO₄ acetonitrile (AN), a mixture of butylene carbonate (BC) and propylene carbonate (PC) and poly2-hydroxyethylmethacrylate gel containing BC and PC. The electron transfer processes within the films can be treated apparently as diffusional processes characterized by the rate constants of the apparent diffusion coefficient (D_app). The value of D_app increase from 1.0 × 10^?9 to 1.6 × 10^?8 cm² sec^?1 as the Fe complex concentration (C_Fe) increases from 0.06 to 1.04 M for the [Fe(AP)₃] complex film (Φ=0.80 μm) in 0.2 M NaClO₄/AN solution. The D_app value for the [Fe(APP)₃) complex film (C_Fe = 0.19 M , Φ= 0.78 μm) is 3.5 × 10^?9 cm² sec^?1 in 0.2 M NaClO₄/AN solution. The D_app values of the [Fe(AP)₃] complex film in the PC + BC mixture and gel containing 1.0 M NaClO₄ were smaller than those obtained in AN solution by an order of magnitude. The dependence of the apparent formal potential of the Fe(II/III) redox reaction for the [Fe(AP)₃] complex film on the activity of NaClO₄ supporting electrolyte in AN shows that Na⁺ moves preferentially across the polymer/solution interfaces during the redox reaction. The Fe(II/III) redox reaction of the Fe complex films shows reversible electrochromic response between red and colorless.