Catalytic Activity For Ethylene Polymerization Research Articles

Straightforward Design for Phenoxy-Imine Catalytic Activity in Ethylene Polymerization: Theoretical Prediction

The quantitative structure-activity relationship (QSAR) of 18 Ti-phenoxy-imine (FI-Ti)-based catalysts was investigated to clarify the role of the structural properties of the catalysts in polyethylene polymerization activity. The electronic properties of the FI-Ti catalysts were analyzed based on density functional theory with the M06L/6-31G** and LANL2DZ basis functions. The analysis results of the QSAR equation with a genetic algorithm showed that the polyethylene catalytic activity mainly depended on the highest occupied molecular orbital energy level and the total charge of the substituent group on phenylimine ring. The QSAR models showed good predictive ability (R2) and R2 cross validation (R2cv) values of greater than 0.927. The design concept is “head-hat”, where the hats are the phenoxy-imine substituents, and the heads are the transition metals. Thus, for the newly designed series, the phenoxy-imine substituents still remained, while the Ti metal was replaced by Zr or Ni transition metals, entitled FI-Zr and FI-Ni, respectively. Consequently, their polyethylene polymerization activities were predicted based on the obtained QSAR of the FI-Ti models, and it is noteworthy that the FI-Ni metallocene catalysts tend to increase the polyethylene catalytic activity more than that of FI-Zr complexes. Therefore, the new designs of the FI-Ni series are proposed as candidate catalysts for polyethylene polymerization, with their predicted activities in the range of 35,000–48,000 kg(PE)/mol(Cat.)·MPa·h. This combined density functional theory and QSAR analysis is useful and straightforward for molecular design or catalyst screening, especially in industrial research.

Bis(imino)pyridines Incorporating Doubly Fused Eight-Membered Rings as Conformationally Flexible Supports for Cobalt Ethylene Polymerization Catalysts

Five distinct α,α′-bis(arylimino)-2,3:5,6-bis(hexamethylene)pyridine-cobalt(II) chloride complexes, [2,3:5,6-{C5H10C(NAr)}2C5HN]CoCl2 (Ar = 2,6-Me2C6H3, Co1; 2,6-Et2C6H3, Co2; 2,6-i-Pr2C6H3, Co3; 2,4,6-Me3C6H2, Co4; 2,6-Et2-4-MeC6H2, Co5), have been synthesized by one-pot template reaction of α,α′-dioxo-2,3:5,6-bis(hexamethylene)pyridine with the corresponding aniline and cobalt(II) chloride in acetic acid. The molecular structures of Co2 and Co3 reveal distorted square pyramidal geometries with two conformationally flexible eight-membered rings, a feature of the ligand manifold. On activation with either methylaluminoxane (MAO) or modified MAO (MMAO), all five complexes displayed high catalytic activities for ethylene polymerization (up to 3.62 × 106 g PE mol–1 (Co) h–1) generating strictly linear polyethylenes with the activity decreasing in the orders: Co4 > Co5 > Co1 > Co2 > Co3 (MAO) and Co1 > Co4 > Co2 > Co5 > Co3 (MMAO). Moreover, the nature of the aluminoxane cocatalyst employed had a marked effec...

Synthesis and Structural Analysis of (Imido)vanadium Dichloride Complexes Containing 2-(2'-Benz-imidazolyl)pyridine Ligands: Effect of Al Cocatalyst for Efficient Ethylene (Co)polymerization.

(Imido)vanadium(V) dichloride complexes containing 2-(2′-benzimidazolyl)-6-methylpyridine ligand (L) of type V(NR)Cl2(L) [R = 1-adamantyl (Ad, 1), C6H5 (2), and 2,6-Me2C6H3 (3)] have been prepared, and their structures were determined by X-ray crystallography as distorted trigonal bipyramidal structures around vanadium. Reactions with ethylene using 1–3 in the presence of methylaluminoxane (MAO) afforded a mixture of oligomer and polymers, and the compositions were affected by the imido ligand employed. By contrast, 1–3 exhibited remarkable catalytic activities for ethylene polymerization in the presence of Me2AlCl; the phenylimido complex (2) exhibited the highest activity [80 100 kg-PE/mol-V·h turn over frequency (TOF, 2 850 000 h–1, 792 s–1)]. The ethylene copolymerizations with norbornene afforded ultrahigh-molecular-weight copolymers with uniform molecular weight distributions and compositions [e.g., Mn = 1.71–2.66 × 106, Mw/Mn = 2.27–2.53]. On the basis of V nuclear magnetic resonance (51V NMR), electron spin resonance, and V K-edge X-ray absorption near-edge structure (XANES) spectra of the catalyst solution, the observed difference in the catalyst performance in the presence of (between) MAO and Me2AlCl cocatalyst should be due to the formation of different catalytically active species with different oxidation states. Apparent changes in the oxidation state were observed in the (especially in the NMR and XANES) spectra upon addition of Me2AlCl, whereas no significant changes in the spectra were observed in presence of MAO.

Pressure-Sensitive Supported FI Catalyst for the Precise Synthesis of Uni- and Bimodal Polyethylene

Pressure-sensitive phenoxy-imine titanium catalyst (FI-catalyst) was successfully synthesized by covalently immobilizing it on the surface of functionalized polystyrene (PS) nanoparticles, which acted as a support and a giant ligand simultaneously. The supported catalyst shows high catalytic activities in ethylene polymerization. Utilizing this catalyst, a serious of unimodal polyethylenes with tailored molecular weights ranging from 2 000 000 to 300 000 were produced under various reaction pressures and temperatures. Particularly, when the polymerization pressure was shifted during the reaction, the ethylene polymer with bimodal molecular weight distribution was successfully synthesized in only a single reactor. Differential scanning calorimetry analysis of the resultant polyethylene revealed a large difference between crystallinities at the first and second heating cycles, indicating that the synthesized polyethylene is of low entanglement.

Integrated synthesis of metallocene@support catalysts based on glyphosate and its zirconium derivatives

Three new kinds of composite metallocene catalyst, Cp2Zr@Gly, Cp2Zr@ZrGp and Cp2Zr@EXZrGP, were synthesized and their catalytic activity in ethylene polymerization was studied.

From polyethylene waxes to HDPE using an α,α'-bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridyl-chromium(iii) chloride pre-catalyst in ethylene polymerisation.

Five examples of α,α'-bis(arylimino)-2,3:5,6-bis(pentamethylene)pyridyl-chromium(iii) chlorides (aryl = 2,6-Me2Ph Cr1, 2,6-Et2Ph Cr2, 2,6-i-Pr2Ph Cr3, 2,4,6-Me3Ph Cr4, 2,6-Et2-4-MePh Cr5) have been synthesized by the one-pot template reaction of α,α'-dioxo-2,3:5,6-bis(pentamethylene)pyridine, CrCl3·6H2O and the corresponding aniline. The molecular structures of Cr1 and Cr4 reveal distorted octahedral geometries with the N,N,N-ligand adopting a mer-configuration. On activation with an aluminium alkyl co-catalyst, Cr1-Cr5 exhibited high catalytic activities in ethylene polymerization and showed outstanding thermal stability operating effectively at 80 °C with activities up to 1.49 × 107 g of PE (mol of Cr)-1 h-1. Significantly, the nature of the co-catalyst employed had a dramatic effect on the molecular weight of the polymeric material obtained. For example, using diethylaluminium chloride (Et2AlCl) in combination with Cr4 gave high density/high molecular weight polyethylene with broad molecular weight distributions (30.9-39.3). By contrast, using modified methylaluminoxane (MMAO), strictly linear polyethylene waxes of lower molecular weight and narrow molecular weight distribution (1.6-2.0) were obtained with vinyl end-groups.

Synthesis and structural analysis of niobium(V) complexes containing amine triphenolate ligands of the type, [NbCl(X)(O-2,4-R2C6H2-6-CH2)3N] (R = Me, tBu; X = Cl, CF3SO3), and their use in catalysis for ethylene polymerization

Niobium(V) dichloride complexes containing amine triphenolate ligands, [NbCl2{(O-2,4-R2C6H2-6-CH2)3N}] [R=Me (1), tBu (2)], and their mono triflate analog, [NbCl(CF3SO3)(O-2,4-R2C6H2-6-CH2)3N] [R=Me (4), tBu (5)] have been prepared, and structures of complexes 1 and 5 have been determined by X ray crystallography; these complexes fold a distorted octahedral geometry around Nb. Complexes 1 and 2 exhibited catalytic activities for ethylene polymerization in the presence of MAO, and the activity markedly increased at high temperature (100, 120°C); 2 showed the higher activities than 1 (activity by 2 in n-octane at 100°C: 576kg-PE/mol-Nb·h).

Synthesis and Structural Analysis of Zr–Al Heterobimetallic Complexes, [ZrX{(O-2,4-tBu2C6H2-6-CH2)3(μ2-O-2,4-tBu2-C6H2-6-CH2)}N][R2Al(μ2-OiPr)] [X = Cl, Et, iBu; R = Me, Et, iBu]. Unique Reactivity of the iBu Complex

A series of heterobimetallic Zr–Al complexes, [ZrCl{(O-2,4-tBu2C6H2-6-CH2)3(μ2-O-2,4-tBu2-C6H2-6-CH2)}N][R2Al(μ2-OiPr)] [R = Me (3), Et (4)] and [ZrR{(O-2,4-tBu2C6H2-6-CH2)3(μ2-O-2,4-tBu2-C6H2-6-CH2)}N][R2Al(μ2-OiPr)] [R = Et (5), iBu (6)], have been prepared by reactions of Zr(OiPr)[(O-2,4-tBu2C6H2-6-CH2)3N] (1) with 1.0 equiv of Al alkyls (Me2AlCl, Et2AlCl, AlEt3, and AliBu3), and their structures (3, 5, 6) were determined by X-ray crystallography. The isobutyl complex (6) is stable in C6D6 and toluene-d6 at 45 °C; the thermolysis of 6 at >60 °C gradually afforded 1 with liberation of AliBu3. These complexes exhibited remarkable catalytic activities for ethylene polymerization at 80–120 °C in the presence of MAO; only complex 6 exhibited the high activity even at 45–60 °C.

1,2-Azaborolyl-Ligated Titanium(IV) Half-Metallocenes: Synthesis, Characterization, and Catalytic Activity in Ethylene Polymerization

The synthesis and characterization of 1,2-azaborolyl (Ab)-ligated titanium(IV) half-metallocene complexes are presented, and their catalytic properties in ethylene polymerization have been evaluated. Mono-Ab TiCl3 complexes 3 and 4 can be conveniently converted to other half-metallocene derivatives (5–8) in moderate to good yields. The molecular structures of titanium complexes 3–8 have been determined by X-ray diffraction analysis. Upon activation with methylaluminoxanes (MAO), mono-Ab Ti half-metallocenes demonstrated high catalytic activity in ethylene polymerization (1.50 × 107 g of PE (mol of Ti)−1 h–1) at a low [MAO] (Al:Ti = 30) .

Pentamethylcyclopentadienyltitanium aryl(pyridyl)amide complexes: Synthesis, characterization and catalytic performance for olefin polymerization

A series of new half-sandwich pentamethylcyclopentadienyl titanium (IV) aryl(pyridyl)amide complexes, Cp*TiCl2[N(Ar)(2-Py)] [Ar = 2,6-iPr2Ph (1), 2,6-Et2Ph (2), 2,6-Me2Ph (3), 4-MePh (4)], have been synthesized from the reactions of Cp*TiCl3 with the lithium salts of the corresponding aryl(pyridyl)amido ligands in toluene. A byproduct with two aryl(pyridyl)amido ligands, Cp*TiCl[N(4-MePh)(2-Py)]2 (5) was also obtained from the synthetic reaction of complex 4 in a small amount. The new titanium complexes 1–4 were characterized by 1H and 13C NMR and elemental analyses. The molecular structures of complexes 1, 2, 4 and 5 were determined by single-crystal X-ray diffraction analysis. X-ray crystallographic analysis on complexes 1, 2, 4 demonstrates that these complexes possess a relatively crowded hepta-coordinating environment surrounding the central titanium atom. Upon activation with AliBu3 and Ph3CB(C6F5)4, complexes 1–4 exhibited moderate to high catalytic activity for ethylene and propylene polymerization, producing high molecular weight linear polyethylene and atactic polypropylene. It was found that complex 1 shows the highest catalytic activity for ethylene polymerization while complex 4 shows the highest catalytic activity for propylene polymerization among these complexes under similar conditions.

Zirconium and hafnium complexes with new tetra-azane ligands: Synthesis, characterization and catalytic properties for ethylene polymerization

Two new anilido-imine tetra-azane ligands, 1,2-[(2′-(ArNH)C6H4HCN)]2C6H4 (Ar=2,6-Me2C6H3 (L1H2) and 2,6-iPr2C6H3 (L2H2)), were synthesized by the condensation reaction of o-phenylenediamine with the corresponding 2-(arylamino)benzaldehyde, and their zirconium and hafnium complexes, L1MCl2 (M=Zr (1b), Hf (1c)) and L2MCl2 (M=Zr (2b), Hf (2c)), were synthesized in high yields (61–66%) by the reactions of L1Li2 and L2Li2 with MCl4 in toluene. Direct HCl-elimination reactions of L1H2 with MCl4 (M=Ti, Zr, Hf) in toluene at 140°C under vacuum afforded the products L1HMCl3 [M=Ti (1a′), Zr (1b′), Hf (1c′)] with a partially deprotonated tridentate ligand in good to high yields (48–70%). All the new complexes were characterized by 1H and 13C NMR spectroscopy and the molecular structures of 1b and 2c were determined by single crystal X-ray diffraction analysis. The metal centers in both complexes are six-coordinated with a distorted octahedral geometry. Upon activation with MAO or AlR3/Ph3CB(C6F5)4, complexes 1b–1c and 2b–2c all exhibit moderate catalytic activity for ethylene polymerization and produce linear polyethylene with ultra-high molar masses (100–184×104g/mol).

Synthesis of Titanium Complexes Containing an Amine Triphenolate Ligand of the Type [TiX{(O-2,4-R2C6H2)-6-CH2}3N] and the Ti–Al Heterobimetallic Complexes with AlMe3: Effect of a Terminal Donor Ligand in Ethylene Polymerization

The synthesis of various titanatranes containing tris(aryloxo)amine ligands, TiX[{(O-2,4-R2C6H2)-6-CH2}3N] [R = Me (1), tBu (2); X = OiPr (a), OtBu (b), OCH(CF3)2 (c), OC(CF3)3 (d), Cl (e)], and some reactions with Al alkyls have been explored. The Ti–Al heterobimetallic complexes [TiMe{(O-2,4-Me2C6H2-6-CH2)2(μ2-O-2,4-Me2-C6H2-6-CH2)}N]-[Me2Al(μ2-OR′)] [R′ = tBu (3b), CH(CF3)2 (3c), C(CF3)3 (3d)] were isolated by reaction of 1b–d with 1 equiv of AlMe3, whereas reaction of 2b with AlMe3 in toluene did not take place under the same conditions, and the reaction of 2c afforded the methyl complex TiMe[{(O-2,4-tBu2C6H2)-6-CH2}3N]. Structures of 3b,c were determined by X-ray crystallography. These complexes exhibited high catalytic activities for ethylene polymerization in n-octane in the presence of MAO, and the activity by 1 and 2 was affected by the terminal donor ligand (X) as well as the substituent on the atrane ligand (R). The activities by 1c,d increased upon addition of AlMe3, and the corresponding hete...

ONNO]-type oxovanadium(V) complexes containing amine pyridine bis(phenolate) ligands: synthesis, characterization and catalytic behavior for ethylene (co)polymerization

A series of oxovanadium(V) complexes bearing dianionic [ONNO] chelate ligands 2-[bis(3-R1-5-R2-2 -hydroxybenzyl) aminomethyl]pyridine (2a: R1=tBu, R2=H; 2b: R1=CF3, R2=H; 2c: R1=OCH3, R2=H; 2d: R1=R2=tBu) and 2-[bis(3-R1-5-R2-2 -hydroxybenzyl) aminoethyl]pyridine (2e: R1=R2=tBu) have been synthesized by reacting VO(OnPr)3 with 1.0 equiv. of the ligands in CH2Cl2. All these complexes were characterized by 1H, 13C, 51V NMR spectra and elemental analysis. X-ray structural analysis for 2d revealed a six-coordinate distorted octahedral geometry around the vanadium center in the solid state. It was observed that these complexes existed as a mixture of two isomers, and the main isomer had the oxo moiety in trans configuration to the tripodal nitrogen atom. In the presence of Et2AlCl and CCl3COOEt, these complexes displayed high catalytic activities for ethylene polymerization even at elevated reaction temperature, depending on ligand structures. The resultant polymers possessed high molecular weights and unimodal molecular weight distributions, indicative of a single active site nature. In addition, copolymerizations of ethylene and norbornene using precatalysts 2a–e were also investigated, and the observed catalytic activity was nearly comparable with that for ethylene homopolymerization. When the concentration of comonomer in the feed amounted to 3.0mol/L, a NBE incorporation up to 41.5% could be achieved. Other reaction parameters that influenced the polymerization behavior, such as reaction temperature and Al/V (molar ratio), are also examined in detail.

Further studies on the effects of substituents at the Cp and salicyladiminato ligands of half-sandwich chromium(III) complexes on their catalytic properties for ethylene polymerization

A series of new half-sandwich chromium(III) complexes Cp′[2-R1-6-(CHNR2)C6H2O]CrCl [R1 = iPr (1), tBu (2, 3, 4, 5); R2 = iPr (2, 4, 5), tBu (1, 3); Cp′ = C5H5(1, 2, 3), C5H2Ph3 (4), C5Me4Ph(5)] were synthesized from the reactions of Cp′CrCl2(THF) with corresponding salicyladiminato lithium. All complexes were characterized by elemental analyses and the structures of complexes 1, 2, 3 and 5 were determined by X-ray diffraction analysis. These complexes show moderate catalytic activities for ethylene polymerization upon activation with a relatively small amounts of AlMe3 or AlEt3, producing high molecular weight polyethylene in the form of spherical particles. Under similar conditions, the catalytic activity of complexes carrying a same salicylaldiminato ligand changes with the cyclopentadienyl ligand in the order Me5Cp > Me4PhCp > 1,2,4-Ph3Cp > Cp. The catalytic activity of these catalysts is also affected significantly by the AlR3 cocatalyst in the order AlMe3 > AlEt3.

New half-sandwich zirconium(IV) complexes containing salicylaldimine ligands: Synthesis, characterizations and catalytic properties

Two new half-sandwich zirconium(IV) complexes bearing salicylaldimine ligands of the type Cp*Zr[2-tBu-4-R-6-(CH=NiPr)C6H2O]Cl2[R=H(1), tBu(2)] were prepared by the reaction of Cp*ZrCl3 with the corresponding lithium of salicylaldimine ligands 2-tBu-4-R-6-(CH=NiPr)C6H2OLi[R=H(LiLa), tBu(LiLb)]. Complexes 1 and 2 were characterized by 1H NMR, 13C NMR spectroscopy and elemental analysis. When activated with AliBu3 and Ph3CB(C6F5)4, both complexes 1 and 2 exhibited reasonable catalytic activities for ethylene polymerization, producing polyethylenes with moderate molecular weight. Complexes 1 and 2 also exhibited reasonable catalytic activities for ethylene copolymerization with 1-hexene, producing poly(ethylene-co-1-hexene)s with moderate molecular weight and reasonable 1-hexene content.

Synthesis, structures of half-sandwich titanium complexes with bulky aryloxide ligand and their catalytic performance for olefin polymerization

Three bulky cyclopentadienyltitanium aryloxide complexes, [Ti(η5-C5Me4Ar)(O-2,6-tBu2C6H3)Cl2], (Ar=C6H5 (4), 4-iPrC6H4 (5), 4-Me3SiC6H4 (6)) have been synthesized from reaction of the corresponding cyclopentadienyltitanium trichloride derivatives with 1 equiv of LiO-2,6-tBu2C6H3. These half-sandwich complexes 4–6 have been characterized by 1H and 13C NMR spectroscopy. The molecular structure of complexes 4 and 6 has been determined by single-crystal X-ray diffraction studies. When activated with iBu3Al and Ph3C+B(C6F5)4−, complexes 4–6 exhibits reasonable catalytic activity for ethylene polymerization, producing moderate molecular weight polyethylenes.

ONN]-type amine pyridine(s) phenolate-based oxovanadium(V) catalysts for ethylene homo- and copolymerization.

A series of oxovanadium(V) complexes containing amine pyridine(s) phenolate ligands [ONN] (2a-f) have been synthesized in high yields (68-83%) by reacting VO(O(n)Pr)3 with 1.0 equiv. of the ligands in CH2Cl2. These complexes were characterized by (1)H, (13)C and (51)V NMR spectroscopy and elemental analysis. X-ray structural analysis for 2a, 2c and 2d revealed that these complexes adopt a six-coordinate distorted octahedral geometry around the vanadium center in the solid state. Upon treatment with Et2AlCl and CCl3COOEt, these complexes displayed high catalytic activities for ethylene polymerization even at elevated reaction temperatures, depending on ligand structures. The resulting polymers possessed high molecular weight and unimodal molecular weight distributions, indicative of the formation of a single catalytically active species during the polymerization catalysis. Excitingly, these vanadium(V) complexes could efficiently promote ethylene/norbornene copolymerization. The observed catalytic activity for the copolymerization was higher than that for ethylene homopolymerization. Moreover, the molecular weights of the resulting copolymers increased upon increasing the norbornene feed. These results indicated that introducing a suitable amount of norbornene into the system not only could accelerate the polymerization rate but also could restrain chain transfer reactions to some extent.

Ethylene (co-)polymerization by long-lifetime half-sandwich zirconium catalyst bearing a [SSO]-carborane ligand

Half-sandwich zirconium complex 3 containing tridentate carborane [S,S,O] ligand 2 [(HOC6H2R2-4,6)(CH2)SC(B10H10) C(Ph)2P=S, R= t Bu] was synthesized by the reaction of CpZrCl3 (Cp= η 5-C5H5) with sodium salt of ligand 2. Zirconium complex 3 was characterized by elemental and NMR analyses. DFT calculations were also performed on complex 3 to analyze the stereochemistry. The results from DFT calculations indicate that structure S1, in which no sulfur atom bonds to the zirconium atom, exists at the lowest energy level. In the presence of methylaluminoxane (MAO), complex 3 exhibited good catalytic activities for ethylene polymerization and long life-time up to 10 h. Moreover, the complex 3/MAO system displayed excellent catalytic activities toword ethylene copolymerization with 1-hexene or polar olefins.

Trinuclear alkyl hydrido rare-earth complexes supported by amidopyridinato ligands: synthesis, structures, C-Si bond activation and catalytic activity in ethylene polymerization.

The reaction of Ap(9Me)Lu(CH2SiMe3)2(thf) (Ap(9Me) = (2,4,6-trimethylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) with two molar equivalents of PhSiH3 affords a trinuclear alkyl-hydrido cluster [(Ap(9Me)Lu)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2]. The analogous reactions with Ap(9Me)Ln(CH2SiMe3)2(thf) (Ln = Y, Yb) are more complex and result in the formation of mixtures of two types of trinuclear alkyl-hydrido complexes [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] and [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiH2Ph)(thf)2] differing in the alkyl group. The DFT calculations of [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] (Ap* = (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) confirm localization of the HOMO on the Ap*-Y(1A)-CH2SiMe3 fragment, thus explaining its enhanced reactivity. Analysis of the electron density distribution reveals the Y-H and H-H bonding interactions in the (Y)3(μ(2)-H)3(μ(3)-H)2 moiety. The NMR studies of diamagnetic complexes [(Ap(9Me)Lu)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] and [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] demonstrated that the trinuclear cores are retained in the solution and revealed exchange between μ(3)- and μ(2)-bridging hydrido ligands. Complexes [(Ap*Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2], the cationic yttrium hydrido cluster [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(thf)3](+)[B(C6F5)4](-) as well as [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] proved to be active in catalysis of ethylene polymerization under mild conditions.

High temperature ethylene polymerization catalyzed by titanium(IV) complexes with tetradentate aminophenolate ligands in cis-O, N, N chelating mode.

A series of titanium trichloride complexes , ligated with claw-type tetradentate aminophenolate ligands were synthesized from the direct reaction of TiCl4(THF)2 with 1 equiv. of the corresponding aminophenol in the presence of triethylamine. For comparison purposes, titanium isopropoxide complexes were also synthesized via the reaction of Ti(O(i)Pr)4 and 1 equiv. of the proligand. Similar reactions of ZrCl4(THF)2 with the corresponding aminophenol ligands in the presence of triethylamine only allowed the isolation of zirconium complex . The X-ray diffraction studies reveal that titanium trichloride complexes , and titanium triisopropoxide complex all possess a distorted octahedral geometry with the tetradentate aminophenolate ligand in cis-O, N, N chelating mode, where the methoxy group of the aryl unit does not coordinate with the metal center in the solid state. Upon activation with MMAO, these titanium and zirconium(iv) complexes exhibited moderate to high catalytic activities for ethylene polymerization at 30-120 °C, producing high-molecular-weight polyethylenes with broad distributions (Mw/Mn = 10.2-34.8). The activities of titanium trichloride complexes are significantly higher than those of titanium isopropoxide and zirconium trichloride complexes at high temperatures. The highest activity of 15 456 kg (mol-Ti h)(-1) could be achieved by titanium trichloride complex with bromo groups on both ortho- and para-positions of the phenolate ring of the ligand at 120 °C.