Activity For Ethylene Polymerization Research Articles

Ethylene Polymerization Activity vs Grafting Affinity Trade-off Revealed by Importance Learning Analysis of In Silico Phillips Catalyst

Ethylene Polymerization Activity vs Grafting Affinity Trade-off Revealed by Importance Learning Analysis of <i>In Silico</i> Phillips Catalyst

Synthesis of functionalized hyperbranched polyethylene with high density polar groups using triarylnaphthyl iminopyridyl palladium catalysts

The 8-arylnaphthalenyl substituent is widely used as an effective chain transfer retarding substituent in late-transition-metal-catalyzed ethylene (co)polymerization. In this contribution, we introduce a new class of palladium catalysts based on 2,4,8-triarylnaphthyliminopyridyl ligands to provide an effective shield on the axial site of the active center. This results in the production of high molecular weight polyethylene or functionalized polyethylene. The palladium catalysts exhibit moderate polymerization activity (104 g mol−1 h−1) in ethylene polymerization. The resulting polyethylene has high molecular weights (16.8–60.8 kg/mol) and high branching densities (90–96/1000C). These catalysts are highly efficient for ethylene and MA copolymerization, enabling access to high molecular weight functionalized polyethylene with a remarkable MA incorporation ratio (9.21–21.00 mol%) under very mild conditions. According to the 13C NMR analysis, it was found that the polyethylene and E-MA copolymers were hyperbranched. In comparison to previously reported iminopyridine palladium catalysts with similar structures, catalysts in this work demonstrated reduced activity and exhibited a relatively high molecular weight, alongside achieving the highest insertion ratio in ethylene (co)polymerization.

Preparation of polyethylene/Siloxene nanocomposites through siloxene‐MgCl supported Ziegler‐Natta catalyst

AbstractThe two‐dimensional (2D) inorganic fillers could significantly improve the properties of polyolefin, thereby satisfying a wider range of applications. Herein, in this research, high‐performance polyethylene (PE)/siloxene nanocomposites were prepared through an in‐situ polymerization with layered siloxene‐supported Ti‐based catalyst. The catalytic ethylene polymerization activity of the siloxene‐supported Ziegler‐Natta catalyst was almost twice that of the MgCl2/TiCl4 catalyst when equal weights of catalysts were used. During the in‐situ polymerization, the layered siloxene fillers exhibited uniform dispersion within the PE matrix. The incorporation of a minimal amount of siloxene filler resulted in a notable enhancement in the thermal stability and mechanical properties of PE. The breaking strength, modulus, elongation at break, and Td5% of PE/siloxene nanocomposites with only 0.71 wt% siloxene were increased by 115.7%, 45.6%, 50.6%, and 58.2°C, respectively. Therefore, this research presents a straightforward method for manufacturing PE with outstanding performance.Highlights PE/siloxene nanocomposites were prepared through in‐situ polymerization. Siloxene is uniformly scattered in the PE matrix. The siloxene and matrix exhibit excellent interfacial adhesion. PE/siloxene nanocomposites with excellent properties were obtained.

Ethylene Polymerizations Catalyzed by Fluorinated "Sandwich" Diimine-Nickel and Palladium Complexes.

Nickel and palladium complexes bearing "sandwich" diimine ligands with perfluorinated aryl caps have been synthesized, characterized, and explored in ethylene polymerization reactions. The X-ray crystallographic analysis of the precatalysts 16 and 6b shows differences from their nonfluorinated analogues 17 and 19, with the perfluorinated aryl caps centered precisely over the nickel and palladium centers, which results in higher buried volumes of the metal centers relative to the nonfluorinated analogues. The sandwich diimine-palladium complexes 5a and 5b containing perfluorinated aryl caps polymerize ethylene in a controlled fashion with activities that are substantially increased compared with their nonfluorinated analogues. Migratory insertion rates in relevant methyl ethylene complexes agree with the activities exhibited in bulk polymerization experiments. DFT studies suggest that facility of ethylene rotation from its preferred orientation perpendicular to the Pd-alkyl bond into a parallel in-plane conformation contributes to the higher polymerization activity for 5b relative to 18a. For these palladium systems, polymer molecular weights can be controlled via hydrogen addition (hydrogenolysis), which is unusual for late-transition-metal-catalyzed olefin polymerizations with no catalyst deactivation occurring. Sandwich diimine-nickel complexes 6a and 6b with perfluorinated aryl caps show ethylene polymerization activities that are about half of those of classical tetraisopropyl-substituted catalyst 2 but again are more active than the analogous nonfluorinated sandwich complexes. Ethylene polymerizations exhibit living behavior, and branched ultrahigh-molecular-weight polyethylenes (UHMWPEs) with very low-molecular-weight distributions (less than 1.1) are obtained. The activated nickel catalysts are stable in the absence of monomer and show good long-term stability at 25 °C.

The synthesis of asymmetrical anilinotropone nickel and palladium complexes for olefin polymerization

For the Coordination-insertion olefin polymerization, the development of high-performance transition-metal catalysts is always the key issue and extensive efforts have been made in this field. In this contribution, we designed several asymmetrical anilinotropone nickel and palladium catalysts. Compared to palladium complex, the nickel catalysts exhibited high activity in ethylene polymerization. The topology microstructure of polyethylene could be modulated by different polymerization temperature. The anilinotropone nickel catalysts Ni2 and Ni3 in this work demonstrated higher thermolability, generating polyethylene with higher molecular weight (up to 285.9 kg mol−1). Moreover, these nickel systems also promoted the copolymerization of ethylene with norbornene-type polar monomers (NB–COOMe, NB-OAc), which demonstrated great polar group tolerance in this system. The generated copolymer exhibited high molecular weight (up to 93.1 kg mol−1) and high polar monomer incorporation ratio (up to 6.9 mol%). The design of asymmetrical anilinotropone catalysts in this work presented a unique form in olefin polymerization and may attract wide application interests in metal catalysis areas.

Non-Symmetrically Fused Bis(arylimino)pyridines with para-Phenyl Substitution: Exploring Their Use as N′,N,N″-Supports in Iron Ethylene Polymerization Catalysis

Through the implementation of a one-pot strategy, five examples of non-symmetrical [N,N-diaryl-11-phenyl-1,2,3,7,8,9,10-heptahydrocyclohepta[b]quinoline-4,6-diimine]iron(II) chloride complexes (aryl = 2,6-Me2Ph Fe1, 2,6-Et2Ph Fe2, 2,6-i-Pr2Ph Fe3, 2,4,6-Me3Ph Fe4, and 2,6-Et2-4-MePh Fe5), incorporating fused six- and seven-membered carbocyclic rings and appended with a remote para-phenyl group, were readily prepared. The molecular structures of Fe2 and Fe3 emphasize the variation in fused ring size and the skewed disposition of the para-phenyl group present in the N′,N,N″-ligand support. Upon activation with MAO or MMAO, Fe1–Fe5 all showed high catalytic activity for ethylene polymerization, with an exceptional level of 35.92 × 106 g (PE) mol−1 (Fe) h−1 seen for mesityl-substituted Fe4/MMAO operating at 60 °C. All catalysts generated highly linear polyethylene with good control of the polymer molecular weight achievable via straightforward manipulation of run temperature. Typically, low molecular weight polymers with narrow dispersity (Mw/Mn = 1.5) were produced at 80 °C (MMAO: 3.7 kg mol−1 and MAO: 4.9 kg mol−1), while at temperatures between 40 °C and 50 °C, moderate molecular weight polymers were obtained (MMAO: 35.6–51.6 kg mol−1 and MAO: 72.4–95.5 kg mol−1). Moreover, analysis of these polyethylenes by 1H and 13C NMR spectroscopy highlighted the role played by both β-H elimination and chain transfer to aluminum during chain termination, with the highest rate of β-H elimination seen at 60 °C for the MMAO-activated system and 70 °C for the MAO system.

Dipicolinate Oxovanadium(IV) Complexes – Well‐Defined, Universal Precatalysts for Ethylene Polymerization and Polar Monomers Oligomerization

AbstractIn the field of polymers and organometallic chemistry, a significant gap is apparent in the area of research on well‐defined metal complexes targeted for using in catalysis leading to olefinic oligomers and polymers. Here, we report on the use in these processes the dipicolinate oxovanadium(IV) complexes, without and with auxiliary ligands, i. e. 1,10‐phenanthroline and 2,2’‐bipyridine. The investigated complexes turned out to be versatile precatalysts. After reaction with appropriate activator, they exhibited 11 times higher a catalytic activity than reference vanadium(IV) complexes with salen ligands – so far, precatalysts from a group of vanadium(IV) complexes with the highest known catalytic activity for polymerization of ethylene. In the case of the oligomerization of polar monomers (2‐chloro‐2‐propen‐1‐ol and 3‐buten‐2‐ol) the complexes described in this report have a catalytic activity (very high) similar to vanadium(IV) complexes known in the literature.

Research Progress of Iron Catalysts with N,N,N‐tridentate Ligands for Ethylene Polymerization

AbstractSome iron complexes are found to be effective catalysts of ethylene polymerization and have become a research hotspot due to their advantages of high activity, good thermal stability, and mild reaction conditions. Compared with other systems, iron catalysts bearing N,N,N‐tridentate ligand have good comprehensive performance in catalyzing ethylene polymerization. This review article focuses on changes in the framework of bis(imino)pyridyl ligand and the effect of different substituents on the catalytic performance of ethylene polymerization (activity, molecular weight, thermal stability, etc.) since 2019. Despite significant achievements, many opportunities and possibilities are yet to be fully addressed, and a brief outlook on the future of issues should be focused on is provided.

Influence of the N–H functionality on activating O,N,N-titanium complexes and controlling polyethylene molecular weights and distributions

Ti complexes supported by O,N,N-ligands show unprecedented activity in ethylene polymerization and produce polymers with unimodal/narrow or bimodal/broad distributions, depending upon amine-N substituents and catalyst pre-activation or not.

Impact of o-aryl halogen effects on ethylene polymerization: steric vs. electronic effects.

Ligand steric hindrance and electronic effects play a crucial role in late-transition metal-catalyzed olefin polymerization. In this research, a series of o-aryl halogenated α-diimine ligands bearing bulky dibenzhydryl substituents, along with their corresponding nickel catalysts, have been synthesized and thoroughly characterized. The nickel catalysts demonstrated very high activity in ethylene polymerization, achieving a high rate of up to 107 g mol-1 h-1. The produced polyethylenes displayed a broad spectrum of molecular weights (12.2-871.7 kg mol-1) but maintained consistent branching densities (50-82/1000 C) when polymerized at a fixed temperature with different nickel catalysts. Notably, the polymerization temperature has a significant influence on both the molecular weight and branching density of the resulting polyethylene. Higher temperatures led to the formation of polyethylenes with lower molecular weights and increased branching densities. Interestingly, the o-aryl halogens significantly impact the molecular weight of the polyethylene. The size of the halogen substituents primarily determines the molecular weight of the polyethylene. However, in terms of branching density, the steric and electronic effects of these substituents appear to counteract each other. In addition, the branched high molecular weight polyethylenes from the bromine and chlorine substituted nickel catalysts are excellent polyethylene thermoplastic elastomers with high strain at break values (688-2478%) and high strain recovery values (42-62%).

Nickel catalysts with asymmetric steric hindrance for ethylene polymerization

α-Diimide catalysts have attracted widespread attention due to their unique chain walking characteristics. A series of α-diimide nickel/palladium catalysts with different electronic effects and steric hindrances were designed and synthesized for olefin polymerization. In this work, we synthesized a series of asymmetric α-diimide nickel complexes with different steric hindrances and used them for ethylene polymerization. These nickel catalysts have high ethylene polymerization activity, up to 6.51×10&lt;sup&gt;6&lt;/sup&gt; g·mol&lt;sup&gt;−1&lt;/sup&gt;·h&lt;sup&gt;−1&lt;/sup&gt;, and the prepared polyethylene has a moderate melting point and high molecular weight (up to 38.2 × 10&lt;sup&gt;4&lt;/sup&gt; g·mol&lt;sup&gt;−1&lt;/sup&gt;), with a branching density distribution between 7 and 94 branches per 1000 carbons. More importantly, the polyethylene prepared by these catalysts exhibits excellent tensile properties, with strain and stress reaching 800% and 30 MPa, respectively.

Catalytic Behavior of Half‐Metallocene Non‐Cp‐Type Group 4 Metal Complexes (M=Zr, Hf) with a Cyclooctatetraenyl Dianion during Olefin Polymerization

AbstractSignificant advancements have been made in metallocene catalysis due to the development of cyclopentadienyl (Cp) ligands by numerous researchers. Furthermore, various ligand combinations have been realized in the last 20 years for the development of post‐metallocene catalysts. Although ligands containing a Cp have been widely reported, only a few reports exist ligands based on other carbon‐only π‐electron moieties. Herein, we focused on the zirconium and hafnium with the 10π‐electron cyclooctatetraenyl (Cot) dianion as an ancillary ligand and investigated the olefin‐polymerization ability of these complexes. Thus, we performed ethylene and ethylene‐1‐octene (co)polymerization using dMAO, MMAO, and Ph3C[B(C6F5)4]/iBu3Al as cocatalysts and confirmed that completion of the polymerization reaction; the catalytic system except dMAO exhibited activities for olefin polymerization to give linear polyethylene or ethylene‐1‐octene copolymer. Furthermore, the zirconium complexes bearing trimethylsilyl‐substituted Cot ligand exhibited enhanced activities for ethylene polymerization compared with an unsubstituted CotZr catalyst.

Exploring Long Range para-Phenyl Effects in Unsymmetrically Fused bis(imino)pyridine-Cobalt Ethylene Polymerization Catalysts

Unsymmetrical 11-phenyl-1,2,3,7,8,9,10-heptahydrocyclohepta[b]quinoline-4,6-dione, incorporating a para-phenyl substituted pyridine unit fused by both 6- and 7-membered carbocyclic rings, has been prepared on the gram-scale via a multi-step procedure involving cyclization, hydrogenation and oxidation. Templating this diketone, in the presence of cobalt(II) chloride hexahydrate, with the corresponding aniline afforded in good yield five examples of doubly fused bis(arylimino)pyridine-cobalt(II) chlorides, Co1 (aryl = 2,6-dimethylphenyl), Co2 (2,6-diethylphenyl), Co3 (2,6-diisopropylphenyl), Co4 (2,4,6-trimethylphenyl) and Co5 (2,6-diethyl-4-methylphenyl). Structural characterization of Co1, Co2 and Co3 highlights the flexible nature of the inequivalent fused rings on the NNN’-ligand and the skewed disposition of the para-phenyl group. On activation with MAO, Co1–Co5 exhibited high activity for ethylene polymerization at 30 °C (up to 5.66 × 106 g (PE) mol−1 (Co) h−1) with the relative order being as follows: Co4 &gt; Co1 &gt; Co5 &gt; Co3 &gt; Co2. All polyethylenes were strictly linear, while their molecular weights and dispersities showed some notable variations. For Co1, Co2, Co4 and Co5, all polymerizations were well controlled as evidenced by the narrow dispersities of their polymers (Mw/Mn range: 1.8–2.7), while their molecular weights (Mw range: 2.9–10.9 kg mol−1) steadily increased in line with the greater steric properties of the N-aryl ortho-substituents. By contrast, the most hindered 2,6-diisopropyl counterpart Co3 displayed a broad distribution with bimodal characteristics (Mw/Mn = 10.3) and gave noticeably higher molecular weight polymer (Mw = 75.5 kg mol−1). By comparison, the MMAO-activated catalysts were generally less active, but showed similar trends in molecular weight and polymer dispersity. End group analysis of selected polymers via 13C and 1H NMR spectroscopy revealed the presence of both saturated and unsaturated polyethylenes in accordance with competing chain transfer pathways. Notably, when comparing Co3/MAO with its non-phenyl substituted analogue (E2,6-iPr2Ph)CoCl2/MAO, the former, though less controlled, displayed higher activity and molecular weight, a finding that points towards a role played by the remote para-phenyl group.

Nitro and 4,4′-flourobenzhydryl functionalized bis(imino)pyridine-cobalt complexes for high molecular weight linear polyethylenes

A series of nitro and 4,4′-fluorobenzhydryl functionalized bis(imino)pyridine-cobalt complexes, [2-{(2,6-iPr2-3-NO2-4-((4-F-Ph)2CH)Ph)N=CMe}-6-{(Ar)N=CMe}C5H5N]CoCl2 (where Ar is 2,6-Me2Ph for Co1; 2,6-Et2Ph for Co2; 2,6-iPr2Ph for Co3; 2,4,6-Me3Ph for Co4; 2,6-Et2-4-Me-Ph for Co5; 2,6-iPr2-3-NO2-4-((4-F-Ph)2CH)Ph for Co6) were prepared and investigated for ethylene polymerization. The resultant compounds were characterized by elemental analysis, 1H/13C NMR and FT-IR spectra. The molecular structure determination revealed a distorted square pyramidal geometry for Co3. All prepared complexes demonstrated high catalytic activity for ethylene polymerization (up to 10.7 × 106 g PE (mol of Co)−1 h−1) and produced high-molecular-weight polyethylenes in the level of 105 g mol−1. Structural variations in the catalyst design revealed that the unsymmetrical complexes with sterically less hindrand substituents exhibited comparatively higher polymerization activity, while sterically encumbered symmetrical complexes proved more efficient in enhancing the molecular weight of resultant polyethylenes. Additionally, high-temperature 1H/13C NMR spectra of the produced polyethylenes confirmed their strictly linear microstructure, which is also evident from their high melting temperature (Tm ∼135 °C).

How does the SiO2-supported nickel catalyst improve the ethylene polymerization process? Insights from DFT studies

Polymerization of ethylene plays a pivotal role in the production of polyethylene, a widely used polymer. Efficient catalysts are crucial for enhancing the polymerization process and improving polymer properties. In this study, we employ density functional theory (DFT) calculations to investigate the influence of the SiO2 surface by linker approach on the reactivity of ethylene polymerization catalyzed by the Ni-α-imine ketone-type complex. Our results unveil valuable insights into molecular interactions and mechanistic aspects driving the improved polymerization process in good agreement with experimental findings. We identify strong hydrogen bonds as the key factor facilitating the favorable binding of the molecular catalyst with the SiO2 surface, involving a chemisorption process. Furthermore, we find that chain initiation is a rate-determining step for the molecular catalyst, whereas chain propagation is rate-determining for the supported catalyst, aligning with experimental differences in ethylene polymerization activity. Energy decomposition analysis reveals the dominant roles of electrostatic and orbital interactions in stabilizing both catalysts. Notably, the chemisorbed catalyst exhibits enhanced catalyst-ethylene interaction, while steric effects primarily impact the reactivity of the homogeneous catalyst. The supported catalyst exhibits a higher propagation barrier due to a late transition state. Additionally, the heterogeneous catalyst demonstrates superior ethylene uptake and thermal stability across a range of temperatures in agreement with the experimental data. These findings offer guidance for future experimental designs, emphasizing the importance of heterogenization and catalyst-ethylene interaction for enhancing ethylene polymerization processes.

Investigations of aryl substituents electronic effects in the catalytic behavior of thermostable α‐diimine nickel (II) catalyst on ethylene polymerization

AbstractIn α‐diimine‐based catalytic systems, it is highly challenging to increase the thermal stability of the α‐diimine Ni(II) catalyst. In this work, we are focused on examining the polymerization of ethylene by a number of α‐diimine Ni(II) complexes with camphyl backbone and various electron‐donating and withdrawing substituents as catalysts. The synthesized camphyl‐based ligands were characterized by 1H nuclear magnetic resonance (NMR), 13C NMR, HH correlation spectroscopy, Fourier‐transform infrared (FT‐IR), and elemental analysis. The formation of the Ni(II) complexes was approved by the far infrared (Far‐IR) and energy dispersive x‐ray spectroscopy (EDS). The Box–Behnken method was used to select the optimal polymerization conditions. The ligand electronic effect on the catalytic activity of Ni(II) complexes in ethylene polymerization was systematically investigated. All of the synthesized complexes were active in ethylene polymerization with activities at 105 g of polyethylenes (PE) (mol of Ni h)−1. The electron‐withdrawing substituent catalyst exhibited high activity in ethylene polymerization.

Significant cooperative effects in binuclear titanium complexes based on trifluoromethyl substituted bis-β-carbonylenamine ligands for ethylene (co)polymerization

The binuclear cooperative effect could greatly improve the catalytic performances for olefin polymerization but has rarely been utilized in early transition nonmetallocene binuclear complexes. Here a series of m- and p-phenylene-bridged bis-β-carbonylenamine ligands and the corresponding binuclear titanium complexes (Ti2mLa-Ti2mLc, Ti2pLa) were synthesized and characterized, with the molecular structure of ligand mLa further characterized by single crystal X-ray diffraction, which indicated that methylthio aniline reacted with the carbonyl next to trifluoromethyl group, thus led to relatively short metal-metal separation in binuclear complexes. Activated by MAO, the binuclear complex Ti2mLa exhibited the highest activity for ethylene polymerization and ethylene/α-olefins copolymerization, and the highest comonomer incorporation, relative to other binuclear Ti2mLb, Ti2mLc and Ti2pLa and mononuclear Ti1La. For ethylene polymerization, the activity of complex Ti2mLa was almost 4 and 2.6 times those of p-phenylene-bridged derivative Ti2pLa and mononuclear Ti1La, and the activity of complex Ti2mLa for ethylene/1-hexene copolymerization was 2 and 4.8 times those of Ti2pLa and Ti1La. Furthermore, the incorporation of comonomer for ethylene/1-hexene copolymerization produced by Ti2mLa was more than twice that of Ti2pLa and triple that of Ti1La. All these results clearly showed that stronger bimetallic cooperative effect existed in binuclear titanium complex Ti2mLa due to shorter metal-metal distance.

Nickel complexes bearing substituted 2-(naphthylen-1-yl)iminopyridines as catalysts for the formation of highly branched unsaturated PE waxes

A set of six 2-iminopyridine-nickel(II) complexes, [2-{C(Me)=NAr}C5H4N]NiCl2 (Ar = 1-C10H7Ni1, 2-Me-1-C10H6Ni2, 2-(CHMePh)-1-C10H6Ni3, 4-(NNC6H5)-1-C10H6Ni4, 4-(NNC6H4-4-Me)-1-C10H6Ni5, 4-(NNC6H4-4-F)-1-C10H6Ni6), all N-functionalized with naphthalen-1-yl or its substituted alkyl or aryldiazenyl derivatives, have been readily synthesized from their corresponding free N,N-ligand, L1 – L6. On crystallization of Ni3, the chloride-bridged trimetallic species, [(L3)3Ni3Cl6(OH2)], was identified as an aqua adduct by single crystal X-ray diffraction. When activated with either MAO or MMAO, high catalytic activity for ethylene polymerization was achieved using Ni1–Ni6 (up to 10.1 × 106 g (PE) mol−1 h−1 for Ni3/MAO), affording low molecular weight polyethylene (Mw range: 0.81–3.50 kg mol−1) with low melting temperature and narrow dispersity. 13C NMR spectroscopic analyses of these polyethylenic waxes revealed the formation of branched macromolecules with branching densities up to 69 per 1000 carbons. Further analysis revealed these polymers to contain predominantly methyl branches (%Me range: 7.8–9.0), with lower levels of longer chain branching and some branch-on branch structure (%sec-Bu range: 0.07–0.12%). Moreover, their 1H and 13C NMR spectra showed various levels of unsaturated functionality in the form of terminal and internal olefins.

Amine-Imine Nickel Catalysts with Pendant O-Donor Groups for Ethylene (Co)Polymerization.

The introduction of a secondary interaction is an efficient strategy to modulate transition-metal-catalyzed ethylene (co)polymerization. In this contribution, O-donor groups were suspended on amine-imine ligands to synthesize a series of nickel complexes. By adjusting the interaction between the nickel metal center and the O-donor group on the ligands, these nickel complexes exhibited high activities for ethylene polymerization (up to 3.48 × 106 gPE·molNi-1·h-1) with high molecular weight up to 5.59 × 105 g·mol-1 and produced good polyethylene elastomers (strain recovery (SR) = 69-81%). In addition, these nickel complexes can catalyze the copolymerization of ethylene with vinyl acetic acid, 6-chloro-1-hexene, 10-undecylenic, 10-undecenoic acid, and 10-undecylenic alcohol to prepare the functionalized polyolefins.

Exploring fluoride effects in sterically enhanced cobalt ethylene polymerisation catalysts; a combined experimental and DFT study.

The fluoro-substituted 2,6-bis(arylimino)pyridine dichlorocobalt complexes, [2-{CMeN(2,6-(Ph2CH)2-3,4-F2C6H)}-6-(CMeNAr)C5H3N]CoCl2 (Ar = 2,6-Me2C6H3 Co1, 2,6-Et2C6H3Co2, 2,6-iPr2C6H3Co3, 2,4,6-Me3C6H2Co4, 2,6-Et-4-MeC6H2Co5), were synthesized in good yield from the corresponding unsymmetrical N,N,N'-ligands, L1-L5. Besides characterization of Co1-Co5 by FT-IR spectroscopy, 19F NMR spectroscopy and elemental analysis, the molecular structures of Co2 and Co5 were also determined highlighting the unsymmetrical nature of the terdentate ligand and the pseudo-square pyramidal geometry about the metal center. When either MAO or MMAO were employed as activators, Co1-Co5 were able to achieve a wide range of catalytic activities for ethylene polymerisation. Co5/MAO exhibited the highest activity of the study at 60 °C (7.6 × 106 g PE mol-1 (Co) h-1) which decreased to 3.3 × 106 g PE mol-1 (Co) h-1 at 80 °C. In addition, it was found that the polymerisation activity increased as the steric hindrance imparted by the ortho groups was enhanced (for MMAO: Co3 > Co5 > Co2 > Co1 > Co4), a finding that was supported by DFT calculations. Furthermore, it was shown that particularly high molecular weight polyethylene could be generated (up to 483.8 kg mol-1) when using Co5/MMAO at 30 °C, while narrow dispersities (M w/M n range: 1.8-4.7) and high linearity (T m > 131.4 °C) were a feature of all polymers produced. By comparison of Co3 with its non-fluorinated analogue using experimental data and DFT calculations, the substitution of fluorides at the meta- and para-positions was demonstrated to boost catalytic activity and improve thermal stability.