Direct synthesis of linear low‐density polyethylene of ethylene/1‐hexene from ethylene with a tandem catalytic system in a single reactor

Tandem catalysis offers a promising synthetic route to the production of linear low‐density polyethylene. This article reports the use of homogeneous tandem catalytic systems for the synthesis of ethylene/1‐hexene copolymers from ethylene stock as the sole monomer. The reported catalytic systems employ the tandem action between an ethylene trimerization catalyst, (η⁵‐C₅H₄CMe₂C₆H₅)TiCl₃ ( 1 )/modified methylaluminoxane (MMAO), and a copolymerization metallocene catalyst, [(η⁵‐C₅Me₄)SiMe₂(^tBuN)]TiCl₂ ( 2 )/MMAO or rac‐Me₂Si(2‐MeBenz[e]Ind)₂ZrCl₂ ( 3 )/MMAO. During the reaction, 1 /MMAO in situ generates 1‐hexene with high activity and high selectivity, and simultaneously 2 /MMAO or 3 /MMAO copolymerizes ethylene with the produced 1‐hexene to generate butyl‐branched polyethylene. We have demonstrated that, by the simple manipulation of the catalyst molar ratio and polymerization conditions, a series of branched polyethylenes with melting temperatures of 60–128 °C, crystallinities of 5.4–53%, and hexene percentages of 0.3–14.2 can be efficiently produced. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4327–4336, 2004     

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.     

Molecular weight control of polyethylene waxes using a constrained imino‐cyclopenta[b]pyridyl‐nickel catalyst

Five examples of nickel(II) bromide complexes bearing N,N‐imino‐cyclopenta[b ]pyridines, [7‐(ArN)‐6,6‐Me₂C₈H₅N]NiBr₂ (Ar = 2,6‐Me₂C₆H₃ ( Ni1 ), 2,6‐Et₂C₆H₃ ( Ni2 ), 2,6‐i‐ Pr₂C₆H₃ ( Ni3 ), 2,4,6‐Me₃C₆H₂ ( Ni4 ), 2,6‐Et₂‐4‐MeC₆H₂ ( Ni5 )), have been prepared by the reaction of the corresponding ligand, L1 – L5 , with NiBr₂(DME) (DME = 1,2‐dimethoxyethane). On crystallization from bench dichloromethane, Ni1 underwent adventitious reaction with water to give the aqua salt, [ L1 NiBr(OH₂)₃][Br] ( Ni1' ). The molecular structures of Ni1' and Ni3 have been structurally characterized, the latter revealing a bromide‐bridged dimer. On activation with either MMAO or Et₂AlCl, Ni1 , Ni2 , Ni4, and Ni5 , all exhibited high activities for ethylene polymerization (up to 3.88 × 10⁶ g(PE) mol^?1(Ni) h^?1); the most sterically bulky Ni3 gave only low activity. Polyethylene waxes are a feature of the materials obtained which typically display low molecular weights (M _ws), narrow M _w distributions and unsaturated vinyl and vinylene functionalities. Notably, the catalyst comprising Ni1 /Et₂AlCl produced polyethylene with the lowest M _w, 0.67 kg mol^?1, which is less than any previously reported data for any class of cycloalkyl‐fused pyridine–nickel catalyst. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3494–3505     

A Tandem Catalytic System for the Synthesis of Ethylene–Hex‐1‐ene Copolymers from Ethylene Stock

Summary: A tandem catalytic system, composed of (η⁵‐C₅H₄CMe₂C₆H₅)TiCl₃ ( 1 )/MMAO (modified methyl aluminoxane) and [(η⁵‐C₅Me₄)SiMe₂(tBuN)]TiCl₂ ( 2 )/MMAO, was applied for the synthesis of ethylene–hex‐1‐ene copolymers with ethylene as the only monomer stock. During the reaction, 1 /MMAO trimerized ethylene to hex‐1‐ene, while 2 /MMAO copolymerized ethylene with the in situ produced hex‐1‐ene to poly(ethylene–hex‐1‐ene). By changing the catalyst ratio and reaction conditions, a series of copolymer grades with different hex‐1‐ene fractions at high purity were effectively produced.

The overall strategy of the tandem 1 / 2 /MMAO catalytic system.     

New Half‐Metallocene Catalysts Generating Polyethylene with Bimodal Molecular Weight Distribution and Syndiotactic Polystyrene

A new type of half‐metallocene catalyst for the polymerization of ethylene and styrene, Cp*M((O)₃O₉Si₇(c‐C₅H₉)₇) (M = Ti ( 1) ; Zr ( 2 )), is prepared by the reaction of (HO)₃O₉Si₇(c‐C₅H₉)₇ with Cp*MCl₃ in the presence of triethylamine. Complex 1 is stable to heat and air, but its heavier congener 2 is slightly air‐sensitive. The catalytic systems 1 /MMAO and 2 /MMAO, in which MMAO is modified methylaluminoxane, show good activities in ethylene polymerization, with that of 2 /MMAO greater than that of 1 /MMAO. Polyethylenes with bimodal molecular weight distributions were obtained. In addition, the catalytic system 1 /MMAO shows fairly good activities for the syndiospecific polymerization of styrene.     

含有NH2CH2CH2CH2NH2和o-C6H4(NH2)2配体的镍配合物的合成、结构和它们在乙烯聚合中的作用

两种镍的配合物[Ni(NH2CH2CH2CH2NH2)3]Cl2 (1)和[Ni(C6H4N2H4)2Cl2] (2)已经被合成并且通过红外和单晶X射线衍射分析对其进行了表征。在配合物1中,镍原子处于手性假八面体[NiN6]的几何构型中,它与三个1,3-丙二胺分子形成了三个六元环。在配合物2中,镍原子除了与两个o-苯二胺分子通过四个Ni-N键形成两个五元环外,它还与两个Cl原子配位形成了反式Ni-Cl2,这不同于以往报道过的镍的二胺配合物。这两个镍的配合物被MAO, MMAO或Et2AlCl活化后,对乙烯的二聚合或三聚合显示了很好的催化活性[对于配合物2,催化活性达到3.59×106 g mol-1 (Ni) h-1]。     

Zirconium‐chelate and mono‐η‐ cyclopentadienyl zirconium‐chelate/ methylalumoxane systems as soluble Ziegler–Natta olefin polymerization catalysts

Zirconium‐chelate and mono‐η‐cyclopentadienyl zirconium‐chelate complexes were tested as ethene and propene polymerization catalysts in combination with methylalumoxane (MAO) as a co‐catalyst: in particular (acac) _nZrCl_4−n (1a–c) (acac = acetylacetonato), (dbm) _nZrCl_4−n (2a–2c) (dbm = dibenzoylmethanato = 1,3‐diphenylpropanedionato) (n = 2–4) and (dbm)₂ZrCl₂(thf) (3) (thf = tetrahydrofuran), (η‐C₅H₅)[H₂B (C₃H₃N₂)₂]ZrCl₂ (4), (η‐C₅H₅)[HB (C₃H₃N₂)₃] ZrCl₂ (5) and (η‐C₅H₅)[(Me₃SiN)₂ CPh]ZrCl₂ (6). Polymerization productivities comparable with the (η‐C₅H₅)₂ZrCl₂ reference system were observed towards ethene for all of the above complexes. In addition, compound 6 showed some minor polymerization activity towards propene. Ethylalumoxane or isobutylalumoxane did not exhibit a co‐catalytic activity for these chelate complexes; in combination with MAO these higher alumoxanes were even found to be deactivating ⁹¹Zr NMR data are reported for 1b, 1c, 4 and 5. Copyright © 2000 John Wiley & Sons, Ltd.     

Dramatic electronic effect of fluoro substituents on the olefin polymerization activity of mono β‐diiminato titanium complexes

A series of new mono β‐diiminato titanium complexes [(N(Ar)C(CH₃))₂ CH]TiCl₃ ( 3a : Ar = 2.6‐F₂C₆H₃; 3b : Ar = C₆F₅; 3c : Ar = 2.6‐Me₂C₆H₃) have been synthesized and characterized. The crystal structure of 3a revealed that the β‐diiminato ligand in our complex is more close to the η²‐coordination mode with little delocalization of the double bonds, which is different from the strong delocalization in the ligands of η⁵‐coordinated (Tolnacnac)TiCl₃ and η²‐coordinated (Dipnacnac)ZrCl₃. The significant electronic effects of fluoro‐substituents on the olefin polymerization activity of mono β‐diiminato titanium complexes were found. Titanium complexes with fluorine‐containing β‐diiminato ligands, on activation with MMAO, are extremely active catalysts for polymerization of ethylene. The activity of copolymerization of ethylene and 1‐hexene is higher than homopolymerization of ethylene and increases with the increase of 1‐hexene concentrations, which show the positive “comonomer effect.” The molar percentage of 1‐hexene incorporation and polymer microstructures can also be modulated by the initial comonomer concentrations. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 211–217, 2008     

Olefin polymerization and copolymerization with soluble transition‐metal complex catalysts

Olefin polymerizations catalyzed by Cp′TiCl₂(O‐2,6‐ⁱPr₂C₆H₃) ( 1 – 5 ; Cp′ = cyclopentadienyl group), RuCl₂(ethylene)(pybox) { 7 ; pybox = 2,6‐bis[(4S)‐4‐isopropyl‐2‐oxazolin‐2‐yl]pyridine}, and FeCl₂(pybox) ( 8 ) were investigated in the presence of a cocatalyst. The Cp*TiCl₂(O‐2,6‐ⁱPr₂C₆H₃) ( 5 )–methylaluminoxane (MAO) catalyst exhibited remarkable catalytic activity for both ethylene and 1‐hexene polymerizations, and the effect of the substituents on the cyclopentadienyl group was an important factor for the catalytic activity. A high level of 1‐hexene incorporation and a lower r_E · r_H value with 5 than with [Me₂Si(C₅Me₄)(N^tBu)]TiCl₂ ( 6 ) were obtained, despite the rather wide bond angle of Cp Ti O (120.5°) of 5 compared with the bond angle of Cp Ti N of 6 (107.6°). The 7 –MAO catalyst exhibited moderate catalytic activity for ethylene homopolymerization and ethylene/1‐hexene copolymerization, and the resultant copolymer incorporated 1‐hexene. The 8 –MAO catalyst also exhibited activity for ethylene polymerization, and an attempted ethylene/1‐hexene copolymerization gave linear polyethylene. The efficient polymerization of a norbornene macromonomer bearing a ring‐opened poly(norbornene) substituent was accomplished by ringopening metathesis polymerization with the well‐defined Mo(CHCMe₂Ph)(N‐2,6‐ⁱPr₂C₆H₃)[OCMe(CF₃)₂]₂ ( 10 ). The key step for the macromonomer synthesis was the exclusive end‐capping of the ring‐opened poly(norbornene) with p‐Me₃SiOC₆H₄CHO, and the use of 10 was effective for this polymerization proceeding with complete conversion. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4613–4626, 2000     

Unique catalytic behavior of chromium complexes having halogenated bis(imino)pyridine ligands for ethylene polymerization

Reactions of CrCl₃(thf)₃ with bis(imino)pyridines gave a series of {bis(imino)pyridine}chromium(III) trichloride complexes, {2,6‐(RN?CMe)₂C₅H₃N}CrCl₃ [R = C₆HPr₂‐2,6 ( 1 ), C₆H₃Et₂‐2,6 ( 2 ), C₆H₃Me₂‐2,6 ( 3 ), C₆H₂Me₃‐2,4,6 ( 4 ), C₆H₃Me₂‐3,5 ( 5 ), C₆H₅ ( 6 ), cyclohexyl ( 7 ), 2‐methyl‐1‐naphthyl ( 8 ), C₆H₃F₂‐2,6 ( 9 ), C₆H₃Br₂‐2,6 ( 10 ), C₆F₅ ( 11 )]. Pseudo‐octahedral geometries of 6 , 10 , and 11 were revealed by X‐ray crystallography. The complexes having bulky substituents such as 1 – 4 showed high activity for ethylene polymerization in combination with modified methylaluminoxane (MMAO) to give linear polyethylenes. In sharp contrast, the pentafluorophenyl complex 11 /modified methylaluminoxane system was found to be moderately active for ethylene homopolymerization to give moderately branched polyethylene with only ethyl branches. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3368–3375, 2005     

Novel P‐Stereogenic PCP Pincer‐Aryl Ruthenium(II) Complexes and Their Use in the Asymmetric Hydrogen Transfer Reaction of Acetophenone

Achiral P‐donor pincer‐aryl ruthenium complexes ([RuCl(PCP)(PPh₃)]) 4c , d were synthesized via transcyclometalation reactions by mixing equivalent amounts of [1,3‐phenylenebis(methylene)]bis[diisopropylphosphine] ( 2c ) or [1,3‐phenylenebis(methylene)]bis[diphenylphosphine] ( 2d ) and the N‐donor pincer‐aryl complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 2). The same synthetic procedure was successfully applied for the preparation of novel chiral P‐donor pincer‐aryl ruthenium complexes [RuCl(P*CP*)(PPh₃)] 4a , b by reacting P‐stereogenic pincer‐arenes (S,S)‐[1,3‐phenylenebis(methylene)]bis[(alkyl)(phenyl)phosphines] 2a , b (alkyl=ⁱPr or ^tBu, P*CHP*) and the complex [RuCl{2,6‐(Me₂NCH₂)₂C₆H₃}(PPh₃)], ( 3 ; Scheme 3). The crystal structures of achiral [RuCl(equation/tex2gif-sup-3.gifPCP)(PPh₃)] 4c and of chiral (S,S)‐[RuCl(equation/tex2gif-sup-6.gifPCP)(PPh₃)] 4a were determined by X‐ray diffraction (Fig. 3). Achiral [RuCl(PCP)(PPh₃)] complexes and chiral [RuCl(P*CP*)(PPh₃)] complexes were tested as catalyst in the H‐transfer reduction of acetophenone with propan‐2‐ol. With the chiral complexes, a modest enantioselectivity was obtained.     

Chloro­bis­(tri­phenyl­phosphine)­nickel(I) tetra­hydro­furan solvate and an unsolvated trigonal phase of chloro­tris­(tri­phenyl­phosphine)­nickel(I)

In [NiCl(C₁₈H₁₅P)₂]·C₄H₈O, the Ni atom is coordinated by three ligands in a distorted trigonal–planar configuration, with a P—Ni—P angle of 111.52 (2)°. In [NiCl(C₁₈H₁₅P)₃], there are three independent mol­ecules in the asymmetric unit, with each Ni—Cl bond on a crystallographic threefold rotation axis. Each Ni centre is tetrahedrally bound. The Ni atoms in both compounds have a d⁹ configuration and a formal oxidation state of Ni^I. A comparison is made between the form of [NiCl(PPh₃)₃] presented here and that of a known toluene solvate.     

Catalytic diversity of diene complexes of niobium and tantalum on polymerizations of ethylene,norbornene, and methyl methacrylate

Half‐metallocene diene complexes of niobium and tantalum catalyzed three‐types of polymerization: (1) the living polymerization of ethylene by niobium and tantalum complexes, MCl₂(η⁴‐1,3‐diene)(η⁵‐C₅R₅) ( 1‐4 ; M = Nb, Ta; R = H, Me) combined with an excess of methylaluminoxane; (2) the stereoselective ring opening metathesis polymerization of norbornene by bis(benzyl) tantalum complexes, Ta(CH₂Ph)₂(η⁴‐1,3‐butadiene)(η⁵‐C₅R₅) ( 11 : R = Me; 12 : R = H) and Ta(CH₂Ph)₂(η⁴‐o‐xylylene)(η⁵‐C₅Me₅) ( 16 ); and (3) the polymerization of methyl methacrylate by butadiene‐diazabutadiene complexes of tantalum, Ta(η²‐RN=CHCH=NR)(η⁴‐1,3‐butadiene)(η⁵‐C₅Me₅) ( 25 : R = p‐methoxyphenyl; 26 : R = cyclohexyl) in the presence of an aluminum compound ( 24 ) as an activator of the monomer.     

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     

Synthesis and cytostatic activity of Pt(II) complexes of intramolecularly coordinated phosphine and stibine ligands

The intramolecularly coordinated phosphine and stibine ligands L¹PPh₂ ( 1 ), L²PPh₂ ( 2 ) and L²SbPh₂ ( 3 ) containing Y,C,Y‐chelating ligands, L¹ = 2,6‐(^tBuOCH₂)₂C₆H₄^? and L² = 2,6‐(Me₂NCH₂)₂C₆H₄^?, were prepared and characterized. The treatment of these ligands 1 , 2 , 3 with PtCl₂ yielded complexes trans‐{[2,6‐(^tBuOCH₂)₂C₆H₃]PPh₂}₂PtCl₂ (4), cis‐{[2,6‐(Me₂NCH₂)₂C₆H₃]PPh₂}PtCl₂ (5), and cis‐{[2,6‐(Me₂NCH₂)₂C₆H₃]SbPh₂}PtCl₂ (6) as the result of different ability of the starting compounds 1 , 2 , 3 to complex platinum centre. Compounds 1 , 2 , 3 , 4 , 5 , 6 were characterized by ¹H, ¹³C and ³¹P NMR spectroscopy and electrospray ionization mass spectrometry, and molecular structures of 3 , 4 , 5 , 6 were determined by X‐ray diffraction analysis. The substitution reactions of complexes 4 , 5 , 6 were also studied. The reaction of 5 and 6 with NaI yielded complexes {[2,6‐(Me₂NCH₂)₂C₆H₃]PPh₂}PtI₂ ( 7 ) and {[2,6‐(Me₂NCH₂)₂C₆H₃]SbPh₂}PtI₂ ( 8 ), while the same reaction of 4 with NaI did not proceed. As the compounds 7 and 8 structurally resemble cisplatin, complex {{[2‐(Me₂NCH₂)‐6‐(Me₂NHCH₂)C₆H₃]PPh₂}PtCl₂}⁺Cl^? ( 9 ) was prepared as water‐soluble platinum complex. The cytotoxic effect of complex 9 was evaluated on human T‐lymphocytic leukemia cells MOLT‐4 (IC₅₀ = 27.6 ± 1.8 µmol l^?1) and human promyelocytic leukemia HL‐60 (IC₅₀ = 55.9 ± 4.9 µmol l^?1). Copyright © 2012 John Wiley & Sons, Ltd.     

Oxidative addition in the coupling of alkylgold(I) with alkyl halides

MeAu(PPh₃) reacts with MeI to afford C₂H₆ and I(PPh₃)Au by a multi-step mechanism involving: (i) oxidative addition to form an intermediate Me₂AuI(PPh₃) species, which (ii), undergoes iodide-methyl exchange with another MeAu(PPh₃) species to afford Me₃Au(PPh₃), followed by (iii), reductive elimination of C₂H₆ and reformation of MeAu(PPh₃). The more reactive trime thylphosphine derivative also readily undergoes (i) oxidative addition and (ii) methyl exchange. However, Me₃Au(PMe₃) is more stable than the PPh₃ analog and does not undergo (iii) reductive elimination. Instead, it is involved in (iv), a further very slow reaction with IAu(PMe₃) and MeI to afford Me₂ AuI(PMe₃) in high yields. C₂H₅Au(PPh₃) specifically affords n-C₄H₁₀ at 0° in MeI. Reactions of other alkylgold(I) complexes with alkyl halides are also reported, and fit into a general mechanistic pattern desribed by reactions (i) – (iv).     

Über die natur der übergangsmetall-kohlenstoff-σ-bindung: IX. Über die darstellung und charakterisierung von η5-cyclopentadienyl-triphenylphosphin-nickel-η1-thioanisolyl und seine thermische zersetzung in nickelthiophenolatokomplexe

The reaction of Cp(PPh₃)NiCl (Cp = η⁵-C₅H₅) with PhSCH₂Li gives Cp(PPh₃)Ni(η¹-CH₂SPh) (I), which has been isolated as green crystals and characterized by elemental analysis, magnetic measurement, ¹H NMR and mass spectroscopic investigations and by protolysis to form PhSCH₃. Cp₂Ni also reacts with PhSCH₂Li in the presence of PPh₃ to give I containing 5–10% of Cp(PPh₃)NiSPh (II) and about 1% of [CpNiSPh]₂ (III) as impurities. In the absence of PPh₃, III is formed, with the release of ethylene and cyclopropane, even at a temperature of ?20°C. For comparison, II has been synthesized from Cp₂Ni, PPh₃ and LiSPh and from the reaction of III with PPh₃.I decomposes in boiling benzene to give II (ca. 33%) and III (ca. 13%). The conversion of the thioanisolyl into thiophenolato complexes can be understood on assuming that {CpNi(η²-CH₂SPh)} is formed as an unstable intermediate.     

Palladium(II) complexes of Y,C,Y‐chelated phosphines: synthesis,structure, and catalytic activity in Suzuki–Miyaura reaction

The phosphines L¹PPh₂ (1) and L²PPh₂ (2) containing different Y,C,Y‐chelating ligands, L¹ = 2,6‐(^tBuOCH₂)₂C₆H₃^? and L² = 2,6‐(Me₂NCH₂)₂C₆H₃^?, were treated with PdCl₂ and di‐µ‐chloro‐bis[2‐[(N,N‐dimethylamino)methyl]phenyl‐C,N]‐dipalladium(II) and yielded complexes trans‐{[2,6‐(^tBuOCH₂)₂C₆H₃]PPh₂}₂PdCl₂ (3), {[2,6‐(Me₂NCH₂)₂C₆H₃]PPh₂} PdCl₂ (4), {[2,6‐(^tBuOCH₂)₂C₆H₃]PPh₂}Pd(Cl)[2‐(Me₂NCH₂)C₆H₄] (5) and {[2,6‐(Me₂NCH₂)₂C₆H₃]PPh₂}Pd(Cl)[2‐(Me₂NCH₂)C₆H₄] (6) as the result of different ability of starting phosphines 1 and 2 to complex PdCl₂. Compounds 3–6 were characterized by ¹H, ¹³C, ³¹P NMR spectroscopy and ESI‐MS. The molecular structures of 3,4 and 6 were also determined by X‐ray diffraction analysis. The catalytic activity of complexes 3–6 was evaluated in the Suzuki‐Miyaura cross‐coupling reaction. Copyright © 2010 John Wiley & Sons, Ltd.     

Facile synthesis of sterically demanding SHOP‐type nickel catalysts for ethylene polymerization

The P,O‐chelated shell higher olefin process (SHOP) type nickel complexes are practical homogeneous catalysts for the industrial preparation of linear low‐carbon α‐olefins from ethylene. We describes that a facile synthetic route enables the modulation of steric hindrance and electronic nature of SHOP‐type nickel complexes. A series of sterically bulky SHOP‐type nickel complexes with variable electronic nature, {[4‐R‐C₆H₄C(O) = C‐PArPh]NiPh (PPh₃); Ar = 2‐[2′,6′‐(OMe)₂C₆H₃]C₆H₄; R = H ( Ni1 ); R = OMe ( Ni2 ); R = CF₃ ( Ni3 )}, were prepared and used as single component catalysts toward ethylene polymerization without using any phosphine scavenger. These nickel catalysts exhibit high thermal stability during ethylene polymerization and result in highly crystalline linear α‐olefinic solid polymer. The catalytic performance of the SHOP‐type nickel complexes was significantly improved by introducing a bulky ortho‐biphenyl group on the phosphorous atom or an electron‐withdrawing trifluoromethyl on the backbone of the ligand, indicating steric and electronic effects play critical roles in SHOP‐type nickel complexes catalyzed ethylene polymerization.     

Preparation of linear α‐olefins to high‐molecular weight polyethylenes using cationic α‐diimine nickel(II) complexes containing chloro‐substituted ligands

A series of α‐diimine nickel(II) complexes containing chloro‐substituted ligands, [(Ar)N?C(C₁₀H₆)C?N(Ar)]NiBr₂ ( 4a , Ar = 2,3‐C₆H₃Cl₂; 4b , Ar = 2,4‐C₆H₃Cl₂; 4c , Ar = 2,5‐C₆H₃Cl₂; 4d , Ar = 2,6‐C₆H₃Cl₂; 4e , Ar = 2,4,6‐C₆H₂Cl₃) and [(Ar)N?C(C₁₀H₆)C?N(Ar)]₂NiBr₂ ( 5a , Ar = 2,3‐C₆H₃Cl₂; 5b , Ar = 2,4‐C₆H₃Cl₂; 5c , Ar = 2,5‐C₆H₃Cl₂), have been synthesized and investigated as precatalysts for ethylene polymerization. In the presence of modified methylaluminoxane (MMAO) as a cocatalyst, these complexes are highly effective catalysts for the oligomerization or polymerization of ethylene under mild conditions. The catalyst activity and the properties of the products were strongly affected by the aryl‐substituents of the ligands used. Depending on the catalyst structure, it is possible to obtain the products ranging from linear α‐olefins to high‐molecular weight polyethylenes. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1964–1974, 2006