Novel bridged bis-azulenyl and bis-tetrahydroazulenyl hafnocenes: Synthesis, structure, and propylene polymerization behavior

Novel bridged bis-azulenyl hafnocenes: dichlorodimethylsilylenebis(2-methyl-4-phenyl-4H-azulenyl) hafnium (4a) and dichlorodimethylsilylenebis[2-ethyl-4-(4-chlorophenyl)-4H-azulenyl] hafnium (4b) were synthesized from 2-methylazulene and 2-ethylazulene, respectively. Hydrogenation of 4a and 4b gave novel bis-tetrahydroazulenyl hafnocenes: dichlorodimethylsilylenebis(2-methyl-4-phenyl-4H-5,6,7,8-tetrahydroazulenyl) hafnium (5a) and dichlorodimethylsilylenebis[2-ethyl-4-(4-chlorophenyl)-4H-5,6,7,8-tetrahydroazulenyl] hafnium (5b). The structures of 4a and 5b were determined by X-ray crystallographic analysis to fold C₂ symmetry. These hafnocenes were found to be active catalysts for propylene polymerization in the presence of methylaluminoxane (MAO), and the preliminary polymerization behavior of these catalysts was evaluated. The melting point and molecular weight of resultant polypropylene were higher than those of the bis-azulenyl zirconocenes. In particular, a high melting point (160 °C for 5a and 161 °C for 5b) was observed with the bis-tetrahydroazulenyl system, although the activities by these hafnocenes were lower than those by the corresponding zirconocenes.     

Titanium complexes with modifiable pyrazolonato and pyrazolonato-ketimine ligands: Synthesis, characterization and ethylene polymerization behavior

Six titanium complexes bearing pyrazolonato and pyrazolonato-ketimine ligands have been synthesized and characterized. It was found that the ligand structure of the synthesized complexes has a significant effect on the catalytic performance of the complexes. The synthesized complexes were activated with MAO and their activities varied from negligible to high (up to 612 kg_PE/(mol_Ti h bar). The pyrazolonato-ketimine complex with a phenyl substituent in the imine part was the most active in the series and it was the only one producing polyethylenes with relatively narrow molecular weight distribution (M_w/M_n from 1.6 to 2.2).     

Group 4 complexes derived from o-carborane: synthesis, structures and ethylene polymerization properties

Nine thermally stable complexes (η⁵-Cp*)[η⁵-(C₅H₄)CMe₂CB₁₀H₁₀CR]MCl₂ (R=H and Me) and (η⁵-Cp*)[η⁵; η¹-(C₅H₄)CMe₂(CB₁₀H₁₀C)]MCl have been prepared via metathesis reactions of Cp*MCl₃ (M=Ti, Zr and Hf, Cp*=pentamethylcyclopentadienyl) with monolithium salts of (C₅H₅)CMe₂(CB₁₀H₁₀CR) (R=H and Me) and with dilithium salt of (C₅H₅)CMe₂(CB₁₀H₁₀CH), respectively. These compounds have been fully characterized by various spectroscopic methods and elemental analyses. All of the compounds except (η⁵-Cp*)[η⁵-(C₅H₄)CMe₂CB₁₀H₁₀CMe]HfCl₂ were additionally characterized by a single crystal X-ray diffraction study, establishing their monomeric bent metallocene structural feature with carborane acting as a substituent or an ancillary ligand. The titanium and zirconium complexes produce high-density polyethylenes with the activity range of about 10³-10⁴ g PE per mol of M bar h in the presence of modified methylaluminoxane cocatalyst.     

Synthesis,structure and catalytic properties of new half-titanocene complexes bearing substituted cyclopentadienyl and aryloxide ligands

New cyclopentadienyltitanium aryloxide complexes, 1-phenyl-2,3,4,5-Me4CpTi(O-2,6-ⁱPr₂-4-ⁿBu-C₆H₂)Cl₂ (1) and [4,4′-biphenyl-(2,3,4,5-Me₄Cp)₂][Ti(O-2,6-ⁱPr₂-4-ⁿBu-C₆H₂)Cl₂]₂ (2), have been prepared by treatment of cyclopentadienyltitanium trichloride complexes [PhMe₄CpTiCl₃ and 4,4′-biphenyl-(Me₄CpTiCl₃)₂] with 1 or 2 equiv of lithium salt of 2,6-di-isopropyl-4-butylphenol. Complexes 1 and 2 have been characterized by elemental analysis, ¹H and ¹³C NMR spectroscopy. The molecular structure of 1 has been determined by single-crystal X-ray diffraction. Upon activation with ⁱBu₃Al and Ph₃CB(C₆F₅)₄, 1 and 2 both exhibit good catalytic activity for ethylene polymerization, producing polyethylene with moderate molecular weight and melting point.     

Synthesis, structure and ethylene polymerization behavior of zirconium complexes with chelating ketoiminate ligands

Mixed ketoiminate/ketoimine/pentamethylcyclopentadienyl (Cp*) complex of zirconium, [(η⁵-Cp*){CH₃C(O)CHC(NHR)CH₃}{CH₃C(O)CHC(NR)CH₃}ZrCl₂] (R=4-CF₃Ph) (3) has been prepared in high yield by the reaction of one equivalent of 4-CF₃-phenyl-β-ketoimine (1a) and one equivalent of lithium 4-CF₃-phenyl-β-ketoiminate (2a) with one equivalent of Cp*ZrCl₃ in Et₂O. Bis(ketoiminate)zirconium dichloride complexes, 4 and 6, have been also prepared in high yield by the reaction of amine elimination of ketoimine ligands, respectively 1a and 1b, with Zr(NMe₂)₄ and followed by chlorination reaction with TMSCl. The X-ray crystallography reveals that the compound 3 is based on distorted octahedral geometry containing a ketoimine and a ketoiminate. The ketoiminate ligand coordinates to the zirconium as a bidentate ligand, leaving the metal center coordinatively unsaturated and thus leading to an additional binding of a ketoimine ligand to the metal to stabilize the complex 3. The zirconium complexes 3, 4 and 6 provide the moderate activity for the polymerization of ethylene in the presence of MMAO cocatalyst. Low molecular weight and high density polyethylene was obtained.     

Synthesis and structures of adamantyl-substituted constrained geometry cyclopentadienyl-phenoxytitanium complexes and their catalytic properties for olefin polymerization

A number of new constrained geometry titanium complexes, [η⁵: η¹-2-C₅Me₄-4-R-6-Ad-C₆H₂O]TiCl₂ [Ad = adamantyl, R = Me (8), ^tBu (9)] and [η⁵: η¹-C₅H₂Ph₂-4-^tBu-6-Ad-C₆H₂O]TiCl₂ (10), were synthesized from reactions of TiCl₄ either directly with corresponding free ligands, 2-C₅Me₄H-4-R-6-Ad-C₆H₂OH [R = Me (5), ^tBu (6)], or with the dilithium salt of the free ligand 2-C₅H₃Ph₂-4-^tBu-6-Ad-C₆H₂OH (7). These new titanium complexes were fully characterized by ¹H and ¹³C NMR spectroscopy and elemental analyses, and the molecular structures of 8 and 9 were determined by single-crystal X-ray crystallography. Upon activation with AlⁱBu₃ and Ph₃CB(C₆F₅)₄ (TIBA/B), these complexes exhibit high catalytic activity for 5-ethylidene-2-norbornene (ENB) polymerization as well as ethylene/1-hexene and ethylene/ENB copolymerization with good tacticity-control ability for the ENB polymerization and high comonomer incorporation ability for the copolymerization reactions. It was found that the bulky adamantyl substituent at the ortho position of the phenoxy group in the ligands of these complexes apparently influences the molecular weight and the microstructure of the resultant polymers.     

Alkyne-functionalized metallocene complexes: Synthesis, structure, and catalytic ethylene polymerization

Reactions of phenylethynyl lithium with substituted cyclopentenones gave the corresponding pendant phenylethynyl substituted cyclopentadienes. Subsequent deprotonation and transmetallation with TiCl₄·2THF, ZrCl₄, and Cp^∗ZrCl₃ yielded the alkyne-functionalized metallocene complexes [C₅Me₄(CCPh)]₂MCl₂ [M = Ti (1), Zr (2)], Cp^∗[C₅Me₄(CCPh)]ZrCl₂ (3), and Cp^∗[C₅H₂R′₂(CCPh)]ZrCl₂ [R′ = Me (4), Ph (5)]. These complexes were fully characterized by ¹H NMR, ¹³C NMR, MS spectra, and elemental analysis. The molecular structure of 2 was determined by single crystal X-ray diffraction analysis. Ethylene polymerization was studied with these complexes in the presence of methylaluminoxane (MAO).     

Lanthanide borohydride complexes with an aryloxide ligand: Synthesis, structural characterization and polymerization activity

Reactions of LnCl₃, NaBH₄ and ArONa (Ar = C₆H₂-t-Bu₃-2,4,6) in a molar ratio of 1:3:1 in THF afforded the aryloxide lanthanide borohydrides of (ArO)Ln(BH₄)₂(THF)₂ (Ln = Yb (1), Er (2)). They were characterized by elemental analysis, infrared spectrum and X-ray crystallography. The two complexes are neutral and isostructural. The lanthanide atom is nine-coordinated by an aryloxide ligand, two borohydride ligands and two THF ligands in a trigonal bipyramidal geometry. Both of the BH₄ ligands in each monomeric complex are η³-coordinated. These complexes displayed moderate high catalytic activities for the polymerization of methyl methacrylate. The polymerization temperature had great influence on the catalysis. At about 0 °C, the catalysts showed the polymerization activity best.     

New binuclear half-titanocene derivatives with aryl-substituted cyclopentadienyl ligands: synthesis,structures, and catalytic properties

Two binuclear oxo-bridged half-titanocene complexes, µ-oxo-bis[(1-aryl-2,3,4,5-tetramethylcyclopentadienyl)dichlorotitanium] [(ArMe₄CpTiCl₂)₂O, Ar?=?4- ⁱ PrC₆H₄ (3), 4- ^t BuC₆H₄ (4)], have been prepared by the treatment of 1-aryl-2,3,4,5-tetramethylcyclopentadienyltitanium trichloride [ArMe₄CpTiCl₃, Ar?=?4- ⁱ PrC₆H₄ (1), 4- ^t BuC₆H₄ (2)] with 0.5?equiv of H₂O. Complexes 3 and 4 have been characterized by elemental analysis and ¹H- and ¹³C-NMR (nuclear magnetic resonance; NMR) spectroscopies, and their molecular structures have been determined by X-ray crystallography. When activated with ⁱ Bu₃Al and Ph₃CB(C₆F₅)₄, complexes 3 and 4 both exhibit reasonable catalytic activity for ethylene polymerization (90?×?10³ to 280?×?10³?kg PE (mol?Ti)^?1?bar^?1?h^?1), producing polyethylenes with moderate molecular weight.     

A series of new zirconium complexes bearing bis(phenoxyketimine) ligands: Synthesis, characterization and ethylene polymerization

A series of new zirconium complexes bearing bis(phenoxyketimine) ligands, bis((3,5-di-tert-butyl-C₆H₂-2-O)R₁CN (2-R₂-C₆H₄))ZrCl₂ {R₁ = Me, R₂ = H (2a); R₁ = Et, R₂ = H (2b); R₁ = Ph, R₂ = H (2c); R₁ = 2-Me-Ph, R₂ = H (2d); R₁ = 2-F-Ph, R₂ = H (2e); R₁ = 2-Cl-Ph, R₂ = H (2f); R₁ = 2-Br-Ph, R₂ = H (2g); R₁ = Ph, R₂ = Me (2h); R₁ = Ph, R₂ = F (2i)}, have been prepared, characterized and tested as catalyst precursors for ethylene polymerization. Crystal structure analysis reveals that complex 2c has a six coordinate center in a distorted octahedral geometry with trans-O, cis-N, cis-Cl arrangement which possesses approximate C₂ symmetry. When activated with methylaluminoxane (MAO), complexes 2a-2i exhibited high ethylene polymerization activities of 10⁶-10⁸ g PE (mol M h)⁻¹. Compared with the bis(phenoxyimine) zirconium analogues bis((3,5-di-tert-butyl-C₆H₂-2-O)CHNC₆H₅)ZrCl₂ (3), the introduction of substituent on the carbon atom of the imine double bond enhanced the catalytic activity and molecular weight of prepared polyethylene. Especially, when the H atom at the carbon atom of the imine double bond was replaced by 2-fluoro-phenyl with strong electronic-withdrawing property, complex 2e displayed the highest catalytic activity, and the polyethylene obtained possessed the highest molecular weight and melt point.     

Nickel (II) complexes bearing 2-ethylcarboxylate-6-iminopyridyl ligands: synthesis, structures and their catalytic behavior for ethylene oligomerization and polymerization

A series of nickel (II) complexes (L)NiCl₂ (7-9) and (L)NiBr₂ (10-12) were prepared by the reactions of the corresponding 2-carboxylate-6-iminopyridine ligands 1-6 with NiCl₂ · 6H₂O or (DME)NiBr₂ (DME = 1,2-dimethoxyethane), respectively. All the complexes were characterized by IR spectroscopy and elemental analysis. Solid-state structures of 7, 8, 10, 11 and 12 were determined by X-ray diffraction. In the cases of 7, 8 and 10, the ligands chelate with the nickel centers in tridentate fashion in which the carbonyl oxygen atoms coordinate with the metal centers, while the carbonyl oxygen atoms are free from coordinating with the nickel centers in 11 and 12. Upon activation with methylaluminoxane (MAO), these complexes are active for ethylene oligomerization (up to 7.97 × 10⁵ g mol⁻¹ (Ni) h⁻¹ for 11 with 2 equivalents of PPh₃ as auxiliary ligand) and/or polymerization (1.37 × 10⁴ g mol⁻¹ (Ni) h⁻¹ for 9). The ethylene oligomerization activities of 7-12 were significantly improved in the presence of PPh₃ as auxiliary ligands. The effects of the coordination environment and reaction conditions on the ethylene catalytic behaviors have been discussed.     

Titanium and zirconium complexes containing sterically hindered hydrotris(pyrazolyl)borate ligands: synthesis, structural characterization, and ethylene polymerization studies

The synthesis, characterization and ethylene polymerization behavior of a set of Tp^′MCl₃ complexes (4, M=Ti, Tp^′=HB(3-neopentyl-pyrazolyl)₃⁻(Tp^Np); 5, M=Ti, Tp^′=HB(3-tert-butyl-pyrazolyl)₃⁻(Tp^tBu); 6, M = Ti, Tp^′=HB(3-phenyl-pyrazolyl)₃⁻(Tp^Ph); 7, M=Zr, Tp^′=HB(3-phenyl-pyrazolyl)₃⁻(Tp^Ph); 8, M=Zr, Tp^′ = HB(3-tert-butyl-pyrazolyl)₃⁻(Tp^tBu)) is described. Treatment of these tris(pyrazolyl)borate Group IV compounds with methylalumoxane (MAO) generates active catalysts for ethylene polymerization. For the polymerization reactions performed in toluene at 60 °C and 3 atm of ethylene pressure, the activities varied between 1.3 and 5.1 × 10³ g of PE/mol[M] · h. The highest activity is reached using more sterically open catalyst precursor 4. The viscosity-average molecular weights () of the PE’s produced with these catalyst precursors varying from 3.57 to 20.23 × 10⁵ g mol⁻¹ with melting temperatures in the range of 127-134 °C. Further polymerization studies employing 7 varying Al/Zr molar ratio and temperature of polymerization showed that the activity as well as the polymer properties are dependent on these parameters. In that case, higher activity was attained at 60 °C. The viscosity-average molecular weights of the polyethylene’s decreases with increasing Al/Zr molar ratio.     

Synthesis, characterization and olefin polymerization of the nickel catalysts supported by [N,S] ligands

The novel nickel (II) complexes (2a, 2b) bearing 1-pyridyl-(3-substituedimidazole-2-thione) ligands were synthesized by the reaction of the corresponding ligands with NiBr₂(DME). 2a and 2b have been characterized by IR, NMR and elemental analysis. The nickel complexes show high catalytic activities for norbornene polymerization in the presence of MAO (methylaluminoxane), although low activities for ethylene polymerization.     

Bridged bis-pyridinylimino dinickel(II) complexes: Syntheses, characterization, ethylene oligomerization and polymerization

A series of bridged bis(pyridinylimino) ligands were efficiently synthesized through the condensation reaction of 4,4′-methylene-bis(2,6-disubstituted aniline) with 2-pyridinecarboxaldehyde or 2-benzoylpyridine. They reacted with (DME)NiBr₂ to form dinuclear Ni(II) complexes. All resultant compounds were characterized by elemental analysis, IR spectra as well as the single-crystal X-ray diffraction to confirm the structures of ligands and complexes. Activated with methylaluminoxane (MAO), these nickel complexes showed considerably good activities for ethylene oligomerization and polymerization. Their catalytic activities and the properties of PEs obtained were depended on the arched environment of ligand and reaction conditions.     

Half-sandwich cyclopentadienyl rhodium complexes bearing pendant sulfur or oxygen ligands and their catalytic behaviors in ethylene polymerization

Two half-sandwich rhodium complexes with sulfur or oxygen functionalized cyclopentadienyl ligands [η⁵-C₅H₄(CH₂)₂SCH₂CH₃]RhI₂3, {[η⁵-C₅H₄(CH₂)₂OCH₃]RhI₂}₂4 have been synthesized and characterized by IR, ¹H-NMR spectra and Elemental analyses. The molecular structures of complexes 3 and 4 have been determined by X-ray crystallographic analysis. Complexes 3, 4 with a pendent arm on cyclopentadienyl ligand have been tested as catalysts for ethylene and norbornene polymerization in the presence of MAO. Complexes 3 and 4 kept high activities of ca. 10⁶ g PE mol⁻¹ Rh h⁻¹ with morderate molecular weight (M_w ≈ 10⁵ g mol⁻¹) of polyethylene in the ethylene polymerization. Catalytic activities, molecular weights of polyethylene have been investigated under the various reaction conditions.     

Titanium(IV) complexes with monocyclopentadienyl and phenoxy-alkoxo ligands: Synthesis,structures and catalytic properties for ethylene polymerization

Three monochlorotitanium complexes Cp′Ti(2,4-^tBu₂-6-(CPh₂O)C₆H₂O)Cl [Cp′ = η⁵-C₅H₅ (2), η⁵-C₅(CH₃)₅ (3), η⁵-C₅H₂Ph₂CH₃ (4)] have been synthesized in high yields (>90%) by the reaction of corresponding Cp′TiCl₃ with the dilithium salt of ligand 2,4-^tBu₂-6-(CPh₂OH)C₆H₂OH (1). When activated by [Ph₃C]⁺[B(C₆F₅)₄]⁻ and AlⁱBu₃, complexes 2–4 exhibit reasonable catalytic activity for ethylene polymerization, producing polyethylenes with moderate molecular weights and melting points. Addition of excess water to complex 2 gave the oxo-bridged complex [Ti(η⁵-C₅H₅)(2,4-^tBu₂-6-(CPh₂O)C₆H₂O)]₂O (5). Complexes 4 and 5 were characterized by single crystal X-ray diffraction.     

Titanium and zirconium complexes containing the new 2,3-dimethyl-1,4-diphenylcyclopentadienyl ligand. Synthesis, characterization and polymerization behavior

An easy and inexpensive three-step synthesis of new 2,3-dimethyl-1,4-diphenylcyclopentadiene (3) ligand and the titanium and zirconium homometallocene dichlorides [TiCl₂(η⁵-C₅H-2,3-Me₂-1,4-Ph₂)₂] (4), [ZrCl₂(η⁵-C₅H-2,3-Me₂-1,4-Ph₂)₂] (5), and the mixed ligand zirconium complex [ZrCl₂(η⁵-C₅H-2,3-Me₂-1,4-Ph₂)(η⁵-C₅H₅)] (6) prepared thereof are described. The polymerization of ethene using 4-6/MAO catalysts revealed that zirconocene complexes 5 and 6 displayed moderate and high activity, respectively, whereas the titanium catalyst 4/MAO was inactive. The crystal structures of 4 and 5 were determined by X-ray crystallography.     

Synthesis and characterization of methyl-phenyl-substituted cyclopentadienyl zirconium complexes

The trisubstituted methyl-phenyl-silyl-cyclopentadienes [Me-Ph-C₅H₃(SiMe₂X)] (X = Me, Cl, NHt-Bu) and [(Me-Ph-C₅H₃)₂SiMe₂] and the lithium salts Li₂[Me-Ph-C₅H₂(SiMe₂Nt-Bu)] and Li₂[(Me-Ph-C₅H₂)₂SiMe₂] have been isolated by conventional methods and characterized by NMR spectroscopy. Desilylation of [Me-Ph-C₅H₃(SiMe₃)] with ZrCl₄(SMe₂)₂ gave the monocyclopentadienyl complex [Zr(η⁵-1-Ph-3-Me-C₅H₃)Cl₃]. The ansa-metallocene [Zr{(η⁵-2-Me-4-Ph-C₅H₂)SiMe₂(η⁵-2-Ph-4-Me-C₅H₂)}Cl₂] was obtained from the mixture of isomers formed by transmetallation of Li₂[(Me-Ph-C₅H₂)₂SiMe₂] to ZrCl₄ and characterized as the meso-diastereomer by X-ray diffraction methods. Similar transmetallation of Li₂[Me-Ph-C₅H₂(SiMe₂Nt-Bu)] gave the silyl-η-amido complex [Zr{η⁵-2-Me-4-Ph-C₅H₂(SiMe₂-η-Nt-Bu)}Cl₂] that was further alkylated to give [Zr{η⁵-2-Me-4-Ph-C₅H₂(SiMe₂-η-Nt-Bu)}R₂] (R = Me, CH₂Ph) and used as a catalyst precursor, activated with MAO, for ethene and propene polymerization. All of the new compounds were characterized by elemental analysis and NMR spectroscopy.     

New anilinotropone-based titanium complexes: synthesis, characterization and application as catalysts for olefin polymerization

New titanium(IV) dichloride complexes containing 2-anilinotropone ligands have been synthesized and characterized. Bis(ligand)titanium dichloride complexes 1 and 2 were synthesized from reaction of TiCl4(THF)2 with 2 equivalents of the corresponding sodium salts of 2-(2,6-diisopropylanilino)tropone (L1) and 2-(2,3,4,5,6-pentafluoroanilino)tropone (L2), respectively. The mixed cyclopentadienyl-anilinotropone compound 3 was synthesized by reaction of the lithium salt of with CpTiCl3. The Cp-mixed micro-O bimetallic complex 4 was also isolated as a by-product owing to the adventitious presence of moisture. The molecular structures 1-4 of have been determined by single-crystal X-ray diffraction studies. Complexes 1 and 2 are isostructural and exhibit a C2-symmetric octahedral geometry, with a trans(N,N), cis(O,O) arrangement in complex 1, but with a trans(O,O), cis(N,N) arrangement in complex 2. The Cp-mixed complex 3 has a distorted square-pyramidal structure with the Cp ligand in the apical position. Bimetallic complex 4 shows a similar coordination geometry for the five-coordinate titanium atom and a pseudo-tetrahedral coordination for the second metallic centre. All new complexes, when activated with methylaluminoxane, are active in the polymerization of ethylene and propene.     

Synthesis of anilinonaphthoquinone-based nickel complexes and their application for olefin polymerization

A series of anilinonaphthoquinone-based nickel complexes, Ni(C₁₀H₅O₂NAr)(Ph)(PPh₃) (Ar = C₆H₃-2,6-Me (1c); Ar = C₆H₂-2,4,6-Me (2c); Ar = C₆H₃-2,6-Et (3c)), were synthesized and the structures of 1c-3c were confirmed by single crystal X-ray analyses. The anilinonaphthoquinone-ligated nickel complexes activated with B(C₆F₅)₃ showed high activities for ethylene polymerization at 40 °C under atmospheric pressure of ethylene and gave polyethylene with long chain branches and short chain branches. The activity of these systems was decreased by lowering polymerization temperature accompanied by increase in molecular weight. The number of the chain branches was also decreased with lowering polymerization temperature and increasing the bulkiness of the ligand.