Homo‐ and copolymerization of ethylene and norbornene with bis(β‐diketiminato) titanium complexes activated with methylaluminoxane

Homo‐ and copolymerization of ethylene and norbornene were investigated with bis(β‐diketiminato) titanium complexes [ArNC(CR₃)CHC(CR₃)NAr]₂TiCl₂ (R = F, Ar = 2,6‐diisopropylphenyl 2a; R = F, Ar = 2,6‐dimethylphenyl 2b ; R = H, Ar = 2,6‐diisopropylphenyl 2c ; R = H, Ar = 2,6‐dimethylphenyl 2d) in the presence of methylaluminoxane (MAO). The influence of steric and electric effects of complexes on catalytic activity was evaluated. With MAO as cocatalyst, complexes 2a–d are moderately active catalysts for ethylene polymerization producing high‐molecular weight polyethylenes bearing linear structures, but low active catalysts for norbornene polymerization. Moreover, 2a – d are also active ethylene–norbornene (E–N) copolymerization catalysts. The incorporation of norbornene in the E–N copolymer could be controlled by varying the charged norbornene. ¹³C NMR analyses showed the microstructures of the E–N copolymers were predominantly alternated and isolated norbornene units in copolymer, dyad, and triad sequences of norbornene were detected in the E–N copolymers with high incorporated content of norbornene. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 93–101, 2008     

Ethylene‐Norbornene Terpolymerization with 5‐Vinyl‐2‐norbornene Using Single‐Site Catalysts

The incorporation of 5‐vinyl‐2‐norbornene (VNB) into ethylene‐norbornene copolymer was investigated with catalysts [Ph₂C(Fluo)(Cp)]ZrCl₂ ( 1 ), rac‐[Et(Ind)₂]ZrCl₂ ( 2 ), and [Me₂Si(Me₄Cp)^tBuN]TiCl₂ ( 3 ) in the presence of MAO by terpolymerizing different amounts of 5‐vinyl‐2‐norbornene with constant amounts of ethylene and norbornene at 60°C. The highest cycloolefin incorporations and highest activity in terpolymerizations were achieved with 1 . The distribution of the monomers in the terpolymer chain was determined by NMR spectroscopy. As confirmed by XRD and DSC analysis, catalysts 1 and 3 produced amorphous terpolymer, whereas 2 yielded terpolymer with crystalline fragments of long ethylene sequences. When compared with poly‐(ethylene‐co‐norbornene), VNB increased both the glass transition temperatures and molar masses of terpolymers produced with the constrained geometry catalyst whereas decreased those for the metallocenes.     

Living copolymerization of ethylene with norbornene mediated by heteroligated (Salicylaldiminato)(β‐enaminoketonato)titanium catalysts

Three heteroligated (salicylaldiminato)(β‐enaminoketonato)titanium complexes [3‐Bu^t‐2‐OC₆H₃CH?N(C₆F₅)][(p‐XC₆H₄)N?C(Bu^t)CHC(CF₃)O]TiCl₂ ( 3a : X = F, 3b : X = Cl, 3c : X = Br) were synthesized and investigated as the catalysts for ethylene polymerization and ethylene/norbornene copolymerization. In the presence of modified methylaluminoxane as a cocatalyst, these unsymmetric catalysts exhibited high activities toward ethylene polymerization, similar to their parallel parent catalysts. Furthermore, they also displayed favorable ability to efficiently incorporate norbornene into the polymer chains and produce high molecular weight copolymers under the mild conditions, though the copolymerization of ethylene with norbornene leads to relatively lower activities. The sterically open structure of the β‐enaminoketonato ligand is responsible for the high norbornene incorporation. The norbornene concentration in the polymerization medium had a profound influence on the molecular weight distribution of the resulting copolymer. When the norbornene concentration in the feed is higher than 0.4 mol/L, the heteroligated catalysts mediated the living copolymerization of ethylene with norbornene to form narrow molecular weight distribution copolymers (M_w/M_n < 1.20), which suggested that chain termination or transfer reaction could be efficiently suppressed via the addition of norbornene into the reaction medium. Polymer yields, catalytic activity, molecular weight, and norbornene incorporation can be controlled within a wide range by the variation of the reaction parameters such as comonomer content in the feed, reaction time, and temperature. ©2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6072–6082, 2009     

A norbornenyl derivative with through‐space ketone π‐interaction

The title compound, endo,exo‐12‐oxotetra­cyclo­[6.2.1.1^3,6.0^2,7]­dodeca‐9‐en‐anti‐11‐yl p‐bromo­benzoate, C₁₉H₁₇BrO₃, con­sists of norbornene with an anti‐p‐bromo­benzoate substituent at the methano bridge and an exo‐fused norbornanone unit bonded to the ethano bridge. The spatially proximate ketone and alkene interact through space and the ketone C atom is substantially pyramidalized. Through‐space ketone π‐inter­action is probably responsible for the low solvolysis rate of the anti‐11‐chloride derivative.     

trans‐Bis­[1‐methyl‐3‐(p‐nitro­phenyl)­triazenido 1‐oxide‐κ2N3,O]­di­pyridine­nickel(II)

In the centrosymmetric title complex, [Ni(C₇H₇N₄O₃)₂(C₅H₅N)₂], the coordination geometry about the Ni²⁺ ion is octahedral, with two deprotonated 1‐methyl‐3‐(p‐nitro­phenyl)­triazenide 1‐oxide ions, viz. [O₂N­C₆H₄­NNN(O)­CH₃]^?, acting as bidentate ligands (four‐electron donors). Two neutral pyridine (py) mol­ecules complete the coordination sphere in positions trans to each other. The triazenide 1‐oxide ligand is almost planar, the largest interplanar angle of 8.80 (12)° being between the phenyl ring of the p‐nitro­phenyl group and the plane defined by the N₃O moiety. The Ni—N_triazenide, Ni—O and Ni—N_py distances are 2.0794 (16), 2.0427 (13) and 2.1652 (18) Å, respectively.     

Ni(II) and Pd(II) complexes bearing benzocyclohexane–ketoarylimine for copolymerization of norbornene with 5‐norbornene‐2‐carboxylic ester

A serial of late transition metal complexes, which bearing Benzocyclohexane–ketoarylimine ligand and named as Mt(benzocyclohexane–ketoarylimino)₂ {Mt(bchkai)₂: Mt=Ni or Pd; bchkai=C₁₀H₈(O)CN(Ar)CH₃; Ar=naphthyl or fluoryl}, have been synthesized and characterized. The molecular structures of the ligands and nickel complex have been confirmed by X‐ray single‐crystal analyses. The nickel complexes exhibited very high activity up to 2.7 × 10⁵ g_polymer/mol_Ni·h and palladium complexes showed high activity up to 2.3 × 10⁵ g_polymer/mol_Pd·h for norbornene (NB) homo‐polymerization with tris(pentafluorophenyl)borane as cocatalyst. The four complexes were effective for copolymerization of NB and 5‐norbornene‐2‐carboxylic acid methyl ester (NB‐COOCH₃) in relatively high activities (0.1–2.4 × 10⁵ g_polymer/mol_Mt·h) and produced the addition‐type copolymers with relatively high molecular weights (0.5 × 10⁵–1.2 × 10⁵ g/mol) as well as narrow molecular weight distributions (PDI < 2 for all polymers). Influences of the metals and comonomer feed content on the polymerization activity as well as on the incorporation rates (20.9–42.6%) were investigated. The achieved NB/NB‐COOCH₃ copolymers were confirmed to be noncrystalline, exhibited good thermal stability (T_d > 400°C) and showed good solubility in common organic solvents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

C–C bridged Ni(II) complexes bearing β‐keto‐9‐fluorenyliminato ligands prepared by different in situ bonding mechanisms and their use in catalytic (co)polymerization of norbornene and styrene

Two C–C bridged Ni(II) complexes bearing β‐keto‐9‐fluorenyliminato ligands with electron‐withdrawing groups (─CF₃), Ni{PhC(O)CHC[N(9‐fluorenyl)]CF₂}₂ (Ni 1 ) and Ni{CF₃C(O)CHC[N(9‐fluorenyl)]Ph}₂ (Ni 2 ), were synthesized by metal coordination reaction and different in situ bonding mechanisms. The C–C bridged bonds of Ni 1 were formed by in situ intramolecular trifluoromethyl and 9‐fluorenyl carbon–carbon cross‐coupling reaction and those of Ni 2 were formed by in situ intramolecular 9‐fluorenyl carbon–carbon radical coupling reaction mechanism. The obtained complexes were characterized using ¹H NMR spectroscopy and elemental analyses. The crystal and molecular structures of Ni 1 and Ni 2 with C–C bridged configuration were determined using X‐ray diffraction. Ni 1 and Ni 2 were used as catalysts for norbornene (NB) polymerization after activation with B(C₆F₅)₃ and the catalytic activities reached 10⁶ g_polymer mol_Ni^?1 h^?1. The copolymerization of NB and styrene catalyzed by the Ni 1 /B(C₆F₅)₃ system showed high activity (10⁵ g_polymer mol_Ni^?1 h^?1) and the catalytic activities decreased with increasing feed content of styrene. All vinyl‐type copolymers exhibited high molecular weight (10⁴ g mol^?1), narrow molecular weight distribution (M_w/M_n = 1.71–2.80), high styrene insertion ratios (11.13–50.81%) and high thermal stability (T_d > 380°C) and could be made into thin films with high transparency in the visible region (400–800 nm).     

ZrIV‐ und TaV‐Komplexe mit methanoverbrückten Bis(aryloxy)‐Liganden

Zr^IV and Ta^V Complexes with Methano‐Bridged Bis(aryloxy) Ligands The bis(aryloxy) ligand precursor compounds bis(2‐trimethylsiloxy‐5‐tbutylphenyl)methane (L–SiMe₃) and its bromoderivative (2‐trimethylsiloxy‐3‐bromo‐5‐tbutylphenyl)(2′‐trimethylsiloxy‐5′‐tbutylphenyl)methane (L^Br–SiMe₃) are prepared in analogy to the corresponding calixarenes in excellent yields. X‐ray structure analysis for L^Br–SiMe₃: space group P2₁/c, a = 12.462(7), b = 10.466(6), c = 23.315(14) Å, β = 105.02(4)°, V = 2937(3) ų, Z = 4. L–SiMe₃ and L^Br–SiMe₃ react with Zr^IV and Ta^V chlorides in very good yields forming di‐ and trinuclear complexes. From the reaction of CpZrCl₃ with L^Br–SiMe₃ in the ratio of 3 : 2 a Zr₃ complex ( 7 ) is obtained, with one L^Br ligand only, which Zr atoms are bridged by a μ₃‐oxygen. The X‐ray structure analysis of 7 (space group R 3, a = 33.23(6), c = 24.47(8) Å, V = 23405(128) ų, Z = 18) additionally reveals that one phenolato oxygen atom of the L^Br ligand is terminally bound to a distorted tetragonal‐pyramidal coordinated Zr atom, while the second phenolato oxygen atom of the L^Br ligand forms a bridge to another Zr atom with a distorted octahedral coordination. The third Zr atom is also found in a distorted octahedral coordination mode. The reactions of L–SiMe₃ and L^Br–SiMe₃ with CpTaCl₄ and TaCl₅ yield dinuclear Ta complexes with a bridging bis(aryloxy) ligand. NMR spectroscopic data point out that the coordination of the bis(aryloxy) ligands in the Ta complexes very much resembles that in the Zr₃‐complex with one terminal and one bridging phenolato oxygen atom. The Zr₃ and the Ta complexes L^BrTa₂Cp₂Cl₆ and LTa₂Cl₈ were tested with respect to their catalytic properties in olefin polymerisation reactions in the presence of MAO.     

Photochromism and decolorization controlled by auxiliary ligands of complexes derived from 1‐methyl‐4,4′‐bipyridinium cation

Three 1‐methyl‐4,4′‐bipyridinium (MQ⁺)‐based complexes, {[Cd(MQ)(p‐BDC)Br]?H₂O}_n ( 1 ), {[Cd(MQ)(m‐BDC)(H₂O)Br]?3H₂O}_n ( 2 ) and Cu(MQ)Br₂ ( 3 ) (p‐H₂BDC = 1,4‐benzenedicarboxylic acid, m‐H₂BDC = 1,3‐benzenedicarboxylic acid), have been synthesized and structurally characterized. Compounds 1 and 2 are one‐dimensional coordination polymers constituted of one coordinated MQ⁺ cation, one coordinated Br^? ion and chains of Cd²⁺ ions connected by deprotonated BDC^2? units, which both have photochromism but different decolorization behaviors. The structures and photoresponsive behaviors controlled by auxiliary ligands have been explored. Compound 3 is constituted of one Cu⁺ center, one MQ⁺ ligand and two coordinated Br^? ions in a ‘V’ configuration, exhibiting no photochromism.     

Vinyl polymerization of norbornene by nickel(II) complexes bearing β‐diketiminate ligands

Norbornene polymerizations were carried out using nickel(II) bromide complexes CH{C(R)NAr}₂NiBr ( 1 , R = CH₃, Ar = 2, 6 ? ⁱPr₂C₆H₃; 2 , R = CH₃, Ar = 2, 6‐Me₂C₆H₃; 3 , R = CF₃, Ar = 2, 6 ? ⁱPr₂C₆H₃; 4 , R = CF₃, Ar = 2, 6‐Me₂C₆H₃) in the presence of methylaluminoxane. Compound 3 is the most active norbornene polymerization catalyst of all the nickel complexes tested. The activity of theses catalysts increases with increases in steric bulk of the substituents on the aryl rings. The electronic nature of the ligand backbone also affects the activity. The resulting polynorbornenes are vinyl type by IR and NMR analyses. Copyright © 2007 John Wiley & Sons, Ltd.     

(M)‐ and (P)‐8‐[(1S,2R)‐2‐hydroxy‐1‐methyl‐2‐phenylethyl]‐8‐methyl‐8,9‐dihydro‐7H‐dinaphth[2,1‐c:1′,2′‐e]azepinium bromide solvates

The title compounds are diastereoisomers with antipodean axial chirality. The M isomer crystallizes as a (1/3) acetone solvate, C₃₂H₃₀NO⁺·Br^?·3C₃H₆O, while the P isomer crystallizes as a (1/1) di­chloro­methane solvate, C₃₂H₃₀NO⁺·Br^?·CH₂Cl₂. In each structure, O—H?Br hydrogen bonds link the cations and anions to give ion pairs. The seven‐membered azepinium ring adopts the usual twisted‐boat conformation and its ring strain causes a slight curvature of the plane of each naphthyl ring.     

Nickel‐Catalyzed Mizoroki–Heck‐ versus Michael‐Type Addition of Organoboronic Acids to α,β‐Unsaturated Alkenes through Fine‐Tuning of Ligands

Various arylboronic acids reacted with activated alkenes in the presence of [Ni(dppe)Br₂], ZnCl₂, and H₂O in CH₃CN at 80 °C to give the corresponding Mizoroki–Heck‐type addition products in good to excellent yields. Furthermore, 1 equivalent of the hydrogenation product of the activated alkene was also produced. By tuning the ligands of the nickel complexes and the reaction conditions, Michael‐type addition was achieved in a very selective manner. Thus, various p‐ and o‐substituted arylboronic acids or alkenylboronic acid reacted smoothly with activated alkenes in CH₃CN at 80 °C for 12 h catalyzed by Ni(acac)₂, P(o‐anisyl)₃, and K₂CO₃ to give the corresponding Michael‐type addition products in excellent yields. However, for m‐substituted arylboronic acids, the yields of Michael‐type addition products are very low. The cause of this unusual meta‐substitution effect is not clear. By altering the solvent or phosphine ligand, the product yields for m‐substituted arylboronic acids were greatly improved. In contrast to previous results in the literature, the present catalytic reactions required water for Mizoroki–Heck‐type products and dry reaction conditions for Michael‐type addition products. Possible mechanistic pathways for both addition reactions are proposed.     

Self‐Assembly,Spectroscopic and Electrochemical Studies of Nickel(II)‐4,8‐Diazaundecanediamide Complex

The self‐assembly of NiCl₂·6H₂O with a diaminodiamide ligand 4,8‐diazaundecanediamide (L‐2,3,2) gave a [Ni(C₉H₂₀N₄O₂)(Cl)(H₂O)] Cl·2H₂O ( 1 ). The structure of 1 was characterized by single‐crystal X‐ray diffraction analysis. Structural data for 1 indicate that the Ni(II) is coordinated to two tertiary N atoms, two O atoms, one water and one chloride in a distorted octahedral geometry. Crystal data for 1: orthorhombic, space group P 21nb, a = 9.5796(3) Å, b = 12.3463(4) Å, c = 14.6305(5) Å, Z = 4. Through NH···Cl–Ni (H···Cl 2.42 Å, N···Cl 3.24 Å, NH···Cl 158°) and OH···Cl–Ni contacts (H···Cl 2.36 Å, O···Cl 3.08 Å, OH···Cl 143°), each cationic moiety [Ni(C₉H₂₀N₄O₂) (Cl)(H₂O)]⁺ in 1 is linked to neighboring ones, producing a charged hydrogen‐bonded 1D chainlike structure. Thermogrametric analysis of compound 1 is consistent with the crystallographic observations. The electronic absorption spectrum of Ni(L‐2,3,2)²⁺ in aqueous solution shows four absorption bands, which are assigned to the ³A_2g → ³T_2g, ³T_2g → ¹Eg, ³T_2g → ³T_1g, and ³A_2g → ³T_1g transitions of triplet‐ground state, distorted octahedral nickel(II) complex. The cyclic volammetric measurement shows that Ni²⁺ is more easily reduced than Ni(L‐2,3,2)²⁺ in aqueous solution.     

Vinyl polymerization of norbornene catalyzed by 2‐Py‐amidine Ni(II) complex/methylaluminoxane systems

Two 2‐Py‐amidine ligands (2‐Py―NH―C(Ph)═N―Ar, Ar = 2,6‐Me₂C₆H₃ and 2,6‐ⁱPr₂C₆H₃) and the corresponding Ni(II) complexes ( 1 and 2 ) were synthesized and characterized using elemental analysis and FT‐IR, UV–visible, ¹H NMR and ¹³C NMR spectroscopies. X‐ray crystal structures indicate that the chelate ring conformation of the less bulky complex 1 is relatively planar compared with that of the bulky complex 2 . Paramagnetic ¹H NMR and ¹³C NMR studies show that, in solution, the time‐average structures of complexes 1 and 2 have mirror symmetry. Both complexes 1 and 2 were used as catalyst precursors for norbornene polymerization with methylaluminoxane as a co‐catalyst. The effects of Al/Ni ratio, temperature and structure of precursors on the catalytic performance were investigated. Copyright © 2014 John Wiley & Sons, Ltd.     

Living regioselective copolymerization of ethylene with nonconjugated bicyclic dienes using (salicylaldiminato)(β‐enaminoketonato) titanium catalysts

A series of heteroligated (salicylaldiminato)(β‐enaminoketonato)titanium complexes [3‐^tBu‐2‐OC₆H₃CH?N(C₆F₅)] [PhN?C(CF₃)CHCRO]TiCl₂ [ 3a : R = Ph, 3b : R = C₆H₄Cl(p), 3c : R = C₆H₄OMe(p), 3d : R = C₆H₄Me(p), 3e : R = C₆H₄Me(o)] were synthesized and characterized. Molecular structures of 3b and 3c were further confirmed by X‐ray crystallographic analyses. In the presence of modified methylaluminoxane as a cocatalyst, these unsymmetric catalysts displayed favorable ability to incorporate 5‐vinyl‐2‐norbornene (VNB) and 5‐ethylidene‐2‐norbornene (ENB) into the polymer chains, affording high‐molecular weight copolymers with high‐comonomer incorporations and alternating sequence under the mild conditions. The comonomer concentration in the polymerization medium had a profound influence on the molecular weight distribution of the resultant copolymer. At initial comonomer concentration of higher than 0.4 mol/L, the titanium complexes with electron‐donating groups in the β‐enaminoketonato moiety mediated room‐temperature living ethylene/VNB or ENB copolymerizations. Polymerization results coupled with density functional theory calculations suggested that the highly controlled living copolymerization is probably a consequence of the difficulty in chain transfer of VNB (or ENB)‐last‐inserted species and some characteristics of living ethylene polymerization under limited conditions. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Bis­[1‐(p‐chloro­phenyl)‐5‐iso­propyl­biguanide‐κ2N2,N4]­nickel(II) dichloride di­methyl­form­amide solvate

The asymmetric unit of the title compound, [Ni(C₁₁H₁₆ClN₅)₂]Cl₂·C₃H₇NO, contains one monomeric nickel(II) com­plex cation, two Cl⁻ anions and one di­methyl­form­amide sol­vent mol­ecule. The Ni atom is coordinated to each of two 1‐­(p‐chloro­phenyl)‐5‐iso­propyl­biguanide (proguanil) ligands via two N atoms. The complex exhibits a square‐planar coordination, with the Ni atom lying 0.021 (2) Å out of the basal plane. The crystal packing is characterized by several hydrogen bonds.     

Novel isolated,L‐amino acid‐ligated rhodium catalysts that induce highly helix‐sense‐selective polymerization of an achiral 3,4,5‐trisubstituted phenylacetylene

Two novel chiral well‐defined rhodium complexes, Rh(cod)(L‐Phe) (cod = 1,5‐cyclooctadiene, Phe = phenylalanine) and Rh(cod)(L‐Val) (Val = valine) were synthesized, isolated by recrystallization, and characterized. The helix‐sense‐selective polymerization (HSSP) of an achiral 3,4,5‐trisubstituted phenylacetylene, p‐dodecyloxy‐m,m‐dihydroxyphenylacetylene (DoDHPA) was examined by using the two Rh complexes as catalysts. These catalysts provided high molecular weight polymers (M_w 28 × 10⁴?45 × 10⁴) in about 40%–85% yields. The resulting polymers exhibited a bisignated CD signal at about 300 nm and a broad signal around 470 nm, indicating that they have preferential one‐handed helical structure. The present catalysts achieved larger molar ellipticity up to [θ]₃₁₀ = 13.0 × 10⁴ deg cm²/dmol than those with binary chiral catalytic systems, [Rh(cod)Cl]₂/(L‐phenylalaninol), [Rh(cod)Cl]₂/(L‐valinol), and [Rh(nbd)Cl]₂/(R)‐PEA. All these results manifest that the present, well‐defined Rh complexes serve as excellent catalysts for the HSSP of DoDHPA. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2346–2351     

Nickel (II) complexes supported by a fluorinated β‐diketiminate backbone ligand: synthesis,catalytic activity toward norbornene polymerization,and the oxygenated species

The reaction of the lithium salt of backbone fluorinated β‐diketiminate ligands, ArNC(CF₃)CHC(CF₃) NArLi, with trans‐[NiCl(Ph)(PPh₃)₂] gives nickel (II) complexes, ArNC(CF₃)CHC(CF₃)NAr(Ph) (PPh₃)Ni (Ar = 2, 6‐Me₂C₆H₃: 1 ; 2, 6‐ⁱPr₂C₆H₃: 2 ). When activated by methylaluminoxane (MAO), both complexes polymerize norbornene rapidly via a vinyl‐type polymerization mechanism. Treatment of nickel complex 1 with oxygen gives rise to intramolecular aerobic hydroxylation. The oxygenated species 3 was characterized by X‐ray crystallography. Copyright © 2006 John Wiley & Sons, Ltd.     

Vinyl/Vinylene functionalized highly branched polyethylene waxes obtained using electronically controlled cyclohexyl‐fused pyridinylimine‐nickel precatalysts

A series of 8‐(2,6‐dibenzhydryl‐4‐R‐phenylimino)‐5,6,7‐trihydroquinoline ligands have been prepared in which the nature of 4‐R substitutions vary from electron withdrawing to electron donating. The treatment with NiCl₂.6H₂O or (DME)NiBr₂ afforded the corresponding complexes of nickel chloride (4‐R = Me Ni1 , Et Ni2 , ^tBu Ni3 , CHPh₂ Ni4 , Cl Ni5 , and F Ni6 ) and nickel bromide (4‐R = Me Ni7 , Et Ni8 , ^tBu Ni9 , CHPh₂ Ni10 , Cl Ni11 , and F Ni12 ). X‐ray diffraction study of complexes Ni3 , Ni6 , and Ni10 , revealed that Ni3.1/2H₂O and Ni6.H₂O adopted unsymmetrical and symmetrical chloride‐bridged dinuclear structures respectively, while Ni10.H₂O is found as mononuclear specie forming distorted‐square planer geometry. In the presence of either diethylaluminum chloride (Et₂AlCl) or modified methylaluminoxane (MMAO), all the nickel complexes ( Ni1–Ni12 ) displayed high activities (up to 1.91 × 10⁶ g(PE) mol (Ni)⁻¹h⁻¹. Highly branched polyethylene waxes with low molecular weights (M_w ≤ 2.6 kg/mol) and narrow molecular weights distributions (M_w/M_n ≤ 1.96) incorporated with vinylene and vinyl groups were obtained. The effects of 4‐R substitutions to the nickel chloride and bromide pre‐catalysts and reaction conditions on the catalytic performance and the properties of the resulting polyethylene were the subject of a detail investigation. The positive influences of using electron‐withdrawing 4‐R substitutions and bromides were observed. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1269–1281     

1‐(2,6‐dibenzhydryl‐4‐fluorophenylimino)‐2‐aryliminoacenaphthylylnickel halides highly polymerizing ethylene for the polyethylenes with high branches and molecular weights

A series of 1‐(2,6‐dibenzhydryl‐4‐fluorophenylimino)‐ 2‐aryliminoacenaphthylene derivatives ( L1–L5 ) and their halonickel complexes LNiX₂ (X = Br, Ni1–Ni5 ; X = Cl, Ni6–Ni10 ) are synthesized and well characterized. The molecular structures of representative complexes Ni2 and Ni4 are confirmed as the distorted tetrahedron geometry around nickel atom by the single crystal X‐ray diffraction. Upon activation with methylaluminoxane, all nickel complexes show high activities up to 1.49 × 10⁷ g of PE (mol of Ni)^?1 h^?1 toward ethylene polymerization, producing polyethylenes with high branches and molecular weights up to 1.62 × 10⁶ g mol^?1 as well as narrow polydispersity. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1369–1378