Catalytic Activity For Polymerization Research Articles

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.

Zirconium Complexes with Bulkier Amine Bis(phenolate) Ligands and Their Catalytic Properties for Ethylene (Co)polymerization.

A series of new zirconium complexes bearing bulkier amine bis(phenolate) tetradentate ligands, Me2NCH2CH2N{CH2(2-O-3-R-5-tBu-C6H2)}2ZrCl2 [R = CPhMe2 (1); CMePh2 (2); CPh3 (3); Ph (4); 3,5-Me2C6H3 (5); 3,5-tBu2C6H3 (6); 4-tBuC6H4 (7)], were synthesized and characterized by 1H nuclear magnetic resonance (NMR), 13C NMR, and elemental analyses. The molecular structures of complexes 1 and 3 were determined by single-crystal X-ray diffraction analysis. The X-ray crystallography analysis reveals that these complexes display a slightly distorted octahedral geometry around their metal centers. Upon activation with methylaluminoxane (MAO), dry-MAO, MAO/butylated hydroxytoluene (BHT), or AliBu3/CPh3B(C6F5)4, these zirconium complexes exhibit high catalytic activity for ethylene polymerization [up to 1.07 × 107 g PE (mol Zr)-1 h-1] and ethylene/1-hexene copolymerization [up to 2.78 × 107 g polymer (mol Zr)-1 h-1], affording (co)polymers with moderate to high molecular weights and good comonomer incorporations. The zirconium complexes with bulkier R groups show higher catalytic activities and longer lifetimes and produce polymers with higher molecular weights, while the zirconium complexes with aryls as R groups demonstrate relatively good comonomer incorporation ability for the copolymerization reactions. These catalytic systems also show moderate catalytic activities for the polymerization reactions of propylene, 1-hexene, and 1-decene. Upon activation with MAO, the zirconium complexes also show moderate catalytic activities for the copolymerization reaction of ethylene with 3-buten-1-ol (treated with 1 equiv of AliBu3), affording copolymers with the incorporation of 3-buten-1-ol up to 1.05%.

Surface activated zinc-glutarate for the copolymerization of CO2 and epoxides.

Zinc-glutarate (ZnGA) is a promising catalyst that can form polymers from CO2 and epoxides, thereby contributing to the development of CO2 utilization technologies and future sustainability. One of the obstacles to commercializing ZnGA in polymer industries is its low catalytic activity. In this study, we introduced activated two-dimensional (2D) ZnGA to improve its catalytic activity in polymerization. The morphology-controlled 2D ZnGA was treated with H3Co(CN)6, and a porous granular-type Co-modified ZnGA (Co-ZnGA) was prepared. The morphology of 2D ZnGA is a prerequisite for the activation by H3Co(CN)6. The catalytic properties of Co-ZnGA were evaluated by copolymerization of various epoxides and CO2, and exhibited catalytic activity of 855, 1540, 1190, and 148 g g-cat-1 with propylene oxide, 1,2-epoxyhexane, 1,2-epoxybutane, and styrene oxide, respectively. This study provided a new strategy using 2D ZnGA instead of conventional ZnGA for increasing the catalytic activity in CO2 polymerization.

Sc and Y bis(alkyl) complexes supported by bidentate and tridentate amidinate ligands. Synthesis, structure and catalytic activity in polymerization of isoprene and 1-heptene

Bis(alkyl) Sc and Y complexes activated with [Ph3C][B(C6F5)4] and AliBu3 provide 40–100% conversion of 500 equivalents of 1-heptene in 24 h to afford the polymer samples with Mn = 1.55–190.2 × 103 and Mw/Mn = 1.55–3.87.

Rare‐Earth Amido and Borohydrido Complexes Supported by Tetradentate Amidinate Ligands: Synthesis, Structure, and Catalytic Activity in Polymerization of Cyclic Esters

Amido [ButC(NC6H4‐2‐OMe)2]2LnN(SiMe3)2 (Ln = Y (3), Nd (4)) and borohydrido complexes [ButC(NC6H4‐2‐OMe)2]2LnBH4 (Ln = Y (5), Nd (6)) coordinated by new amidinate ligand bearing two pendant anisolyl groups are synthesized. According to X‐ray analysis in complexes 3 and 4 one amidinate ligand is coordinated to the Ln3+ cation in a bidentate fashion (κ2‐NN), while the second one is tetradentate (κ4‐NNOO). At the same time in borohydrido neodymium complex 6 the amidinate ligands demonstrate κ4‐NNOO and κ3‐NNO coordination modes. Complexes 3–6 proved to be efficient initiators for ring‐opening polymerization of rac‐lactide and allow for achieving quantitative conversion of 500 equivalents of monomer into polymer in 0.3–4.5 h at 25 °C. The polymerization of ε‐caprolactone initiated by 3–6 proceeds much faster under similar conditions.

Rare-earth complexes supported by an ansa-bis(amidinate) ligand with a rigid o-phenylene linker: synthesis, structure, and catalytic activity for polymerization of cyclic esters.

A bis(amidinate) ligand with a rigid o-phenylene linker C6H4-1,2-[NC(tBu)NH(C6H5)]2 (1) was successfully employed for the syntheses of rare-earth amides 2-5 in good yields. The structures of the amides were established by X-ray diffraction analysis and revealed that the ligand framework coordinated to the lanthanide atoms in different fashions depending on the central ion size. Larger lanthanide metal ions La3+ and Nd3+ prefer to form dinuclear complexes with one linked bis(amidinate) ligand as a bridge, while the smaller sized Y3+ and Er3+ favor the formation of mononuclear complexes. These complexes exhibited good catalytic activity for ring-opening polymerization of ε-caprolactone and l-lactide and the mononuclear complexes display higher activity.

Aluminum complexes with Schiff base bridged bis(indolyl) ligands: synthesis, structure, and catalytic activity for polymerization of rac-lactide.

A series of Schiff base bridged bis(indolyl) ligands were developed for aluminum chemistry. The reactions of AlEt3 or AlMe3 with the Schiff base bridged bis(indolyl) proligands R1(-N[double bond, length as m-dash]CHC8H5NH)2 (R1 = -CH2CH2- (H2L1); -CH2CH2CH2- (H2L2); -CH2CMe2CH2- (H2L3); rac-Cy (H2L4); and R,R-Cy (H2L5)) were studied leading to the synthesis of a series of aluminum alkyl complexes L1AlEt (1)-L5AlEt (5) and L3AlMe (3b) in good yields, while the reaction of H2L3 with Al(OiPr)3 gave the aluminum alkoxide complex L3AlOiPr (3a). These aluminum complexes were characterized by spectroscopic methods and elemental analyses. The solid state structures of the aluminum complexes 1-5 and 3a were confirmed by the X-ray diffraction study. X-ray analyses revealed that the aluminum centre in these complexes is five-coordinated. The coordination geometry is between square pyramidal and trigonal bipyramidal. In the presence of 1 equiv. of isopropanol, the aluminum alkyl complexes exhibited notable activity towards the ring-opening polymerization of rac-lactide at 70 °C in toluene, with good control over molecular weights and dispersities. The substituents and the length of the bridging part between the two Schiff base nitrogen atoms have an influence on either the tacticity of isolated polymers or the rate of polymerization. The kinetics of complex L3AlOiPr (3a) in C6D6 was also investigated, and the experimental results revealed that the rate of polymerization was first-order with respect to rac-lactide.

Synthesis, structure and catalytic polymerization activity of half‐sandwich cyclometallated iridium complexes

A series of mononuclear half‐sandwich cyclometallated iridium complexes with Schiff base ligands were synthesized in good yields. Five air‐stable C,N‐chelate mode complexes were obtained smoothly through metal‐mediated C─H bond activation. Treatments of dimeric metal complexes [Cp*IrCl2]2 with ligands L1–L5 afforded the corresponding C,N‐chelate mononuclear half‐sandwich iridium(III) complexes 1–5. These iridium complexes exhibit high catalytic activity for norbornene polymerization. Both steric and electronic effects of the substituted groups have influences on the behaviors of the polymerization process. All complexes were characterized using infrared and NMR spectroscopies and elemental analysis. Molecular structures of complexes 1, 2 and 5 were further confirmed using single‐crystal X‐ray analysis.

Triketiminate bis(borohydride) complexes of rare-earth metals [(2,6-Me2C6H3N=CMe)2C(2,6-Me2C6H3N=CBut)]Ln(BH4)2(THF)2 (Ln = Y, Nd): synthesis, structure, and catalytic activity in polymerization of rac-lactide, ε-caprolactone, and isoprene

A new triketimine (2,6-Me2C6H3N=CMe)2CH(2,6-Me2C6H3N=CBut) (1) was synthesized by the reaction of imidoyl chloride 2,6-Me2C6H3N=CClBut with lithium diketiminate (2,6-Me2C6H3N=CMe)2CHLi. In the crystalline state, compound 1 exists in the diimineenamine form; in solution, in the triimine form. The metalation of triketimine 1 with n-butyllithium in THF at 0 °C produced lithium triketiminate [(2,6-Me2C6H3N=CMe)2C(2,6-Me2C6H3N=CBut)]Li(THF)2 (2). The metathesis reactions of Ln(BH4)3(THF)3 (Ln = Y, Nd) with compound 2 (1: 1 molar ratio, THF) gave the neutral triketiminate bis(borohydride) complexes [(2,6-Me2C6H3N=CMe)2C(2,6-Me2C6H3N=CBut)]Ln(BH4)2(THF)2 (Ln = Y (3), Nd (4)). As opposed to the complexes with neutral triketimine, the monoanionic triketiminate ligand is coordinated to Li and Y or Nd cations in a bidentate fashion. Complexes 3 and 4 catalyze the polymerization of rac-lactide and e-caprolactone; in combination with [Ph3C][B(C6F5)4] and AlBu3 i (1 : 1 : 10 molar ratio), these compounds exhibit catalytic activity in the polymerization of isoprene.

Yttrium complexes containing heteroscorpionate ligands [(3,5-But 2C3HN2)2CHC(Ph)2O]– and [o-Me2NC6H4CH2C(NCy)2

A reaction of benzophenone with bis(3,5-di-tert-butylpyrazolyl)methyllithium (3,5-But2C3HN2)2CHLi (obtained in situ by metallation of (3,5-But2C3HN2)2CH2 with n-butyllithium in THF at–70 °C) led to the synthesis of alkoxide lithium complex [(3,5-But2-C3HN2)2CHCPh2O]Li(THF) (1) containing a new monoanionic heteroscorpionate ligand [(3,5-But2C3HN2)2CHCPh2O]–. Hydrolysis of complex 1 gave 2,2-bis(3,5-di-tert-butylpyrazolyl)-1,1-diphenylethanol (2) in 90% yield. The structure of alcohol 2 was established by X-ray crystallography. A reaction of anhydrous YCl3 with two molar equivalents of lithium alkoxide 1 in THF furnished yttrium monochloride complex [(3,5-But2C3HN2)2CHCPh2(μ-O)]2-YCl(THF)[(μ-Cl)Li]2 (3). According to X-ray diffraction data, chloride 3 is a monomeric ate-complex with one terminal and two bridging chloride ligands. The nitrogen atoms of the pyrazole rings are not involved in the coordination of the ligand with the yttrium ion. The bisalkyl complex [(3,5-But2C3HN2)2CHCPh2O]Y(CH2SiMe3)2(THF)2 (4) obtained by the reaction of alcohol 2 with an equimolar amount of Y(CH2SiMe3)3(THF)2 turned out to be unstable and completely decomposed in solution in C6D6 at 25 °C within two hours. An exchange reaction of equimolar amounts of YCl3 and {[o-Me2NC6H4CH2C(NCy)2]Li(THF)2}2 (5) (Cy is the cyclohexyl) in THF led to the formation of a neutral monochloride complex [o-Me2NC6H4CH2C(NCy)2]2YCl(THF)2 (6). A reaction of complex 6 with an equimolar amount of o-Me2NC6H4CH2Li in toluene led to the synthesis of a new yttrium aminobenzyl complex [o-Me2NC6H4CH2C(NCy)2]2Y[CH2C6H4-o-NMe2] (7). X-ray diffraction studies showed that in complexes 6 and 7 the donor NMe2 groups of amidinate ligands are not involved in the metal—ligand interaction. Yttrium complexes 4 and 7 exhibited catalytic activity in polymerization of isoprene.

Bisborohydride yttrium complexes containing amidinate ligands [o-Me2NC6H4CH2C(NR)2]Y(BH4)2L n (R = Pri, L = DME, n = 1; R = Cy, L = THF, n = 2). Synthesis, structure, and catalytic activity in polymerization of rac-lactide and isoprene

A reaction of o-N,N-dimethyltoluidine lithium derivative (o-Me2NC6H4CH2Li) with carbodiimides (RN=C=NR, where R = Pri, Cy) in THF at room temperature leads to lithium complex of the general formula [{o-Me2NC6H4CH2C(NR)2}Li(THF)2]2 (R = Pri (1), Cy (2)) containing a new tridentate amidinate ligand. X-ray diffraction studies showed that complexes 1 and 2 are dimeric due to the coordination of the nitrogen atoms of the amidinate group with different lithium atoms. The nitrogen atoms of the aminobenzyl fragment are not involved in the complexation. The exchange reactions of Y(BH4)3(THF)3 with lithium amidinates 1 and 2 carried out with the equimolar ratio of reagents in solution in THF proceeded with the formation of neutral amidinatebisborohydride complexes of the general formula [o-Me2NC6H4CH2C(NR)2]Y(BH4)2Ln (3: R = Pri, L = DME (with added DME), n = 1; 4: R = Cy, L = THF, n = 2). According to the X-ray diffraction data, compounds 3 and 4 are monomeric, borohydride ligands are coordinated to the rare-earth metal atom by the η3- and η2-type. The donor NMe2 groups of the amidinate ligands are not involved in the metal—ligand interaction. Yttrium complexes 3 and 4 exhibit catalytic activity in polymerization of rac-lactide and isoprene.

N,N′,X-bidentate versus N,N′,X-tridentate N-substituted 2-iminomethylpyridine- and 2-iminomethylquinoline-coordinated palladium(II) complexes

The reaction of [Pd(CH3CN)2Cl2] with N-functional group-substituted 2-iminomethylpyridine and 2-iminomethylquinoline can produce N,N′,X-bidentate Pd(II) complexes and N,N′,X-tridentate Pd(II) complexes depending on the functional group substitution on the nitrogen of the imine moiety. For example, N,N-dimethyl-3-((pyridin-2-ylmethylene)amino)propan-1-amine (L1), N,N-dimethyl-3-((quinolin-2-ylmethylene)amino)propan-1-amine (L2), and N-(3-(methylthio)propyl)-1-(pyridin-2-yl)methanimine (L3) were coordinated to palladium as N,N′,X-tridentate mode in the presence of NaClO4 to yield two fused ring metallacyclic [(NN′X)PdCl]ClO4 complexes with high yield, i.e. [LnPdCl]ClO4 (Ln = L1, L2, L3), respectively. However, N-methyl-N-(3-((pyridin-2-ylmethylene)amino)propyl)aniline (L4) and N-(3-methoxypropyl)-1-(pyridin-2-yl)methanimine (L5) yield (in the absence of NaClO4) N,N′,X-bidentate metallacyclic [(NN′)PdCl2] complexes with high yield, i.e. [L4PdCl2] and [L5PdCl2], respectively. The X-ray crystal structure of Pd(II) complexes revealed that the palladium in [LnPdCl]ClO4 (Ln = L1, L2, L3) and [LnPdCl2] (Ln = L4, L5) formed a slightly distorted square planar geometry involving two nitrogens of iminomethylpyridine ligand, one X, and one or two chlorides. The N,N′,X-tridentate complex [L2PdCl]ClO4 and the N,N′,X-bidentate complex [L5PdCl2] showed high catalytic activity for polymerization of methyl methacrylate in the presence of co-catalyst, modified methylaluminoxane at 60 °C compared to the reference complex anhydrous [PdCl2]. Specifically, the activities of [L2PdCl]ClO4 and [L4PdCl2] were 1.43 × 105 and 1.08 × 105 g PMMA M−1 Pd h, respectively. The syndiotacticity of poly(methylmethacrylate) (PMMA), which was characterized using 1H NMR spectroscopy, was about 0.70 for the [L2PdCl]ClO4 and [L4PdCl2] complexes.

Studies on Ring-Opening Metathesis Polymerization of Norborene Catalyzed by Hydride Containing Mononuclear Ruthenium Complex

Ring-opening metathesis polymerization (ROMP) has emerged as an important tool for the preparation of architecturally unique macromolecules from cyclic olefins. A wide variety of catalytic systems, ranging from simple metal salts to highly sophisticated alkylidene metal complexes, have been used for the achievement of this synthetically useful transformation. Especially, tremendous efforts have been directed toward the ruthenium-based catalytic systems as well as the understanding of their reactivity patterns. And Grubbs catalysts represent the ultimate in terms of activity, but they are not cost effective due to the sophisticated ligand. Therefore, alternative catalyst precursors that are more readily accessible have been and are still being actively developed. Therefore, a hydride ligand containing mononuclear ruthenium complex Ru(p-cymene)HClPCy3 reported here was designed to catalyze ring-opening metathesis polymerization of norbornene with high activity. The hydride ligand is critical based on its high trans effect (for ligand dissociation) and the ability to generate carbene species through plausible migratory insertion and α-elimination steps. This catalytic system bearing hydride ligand could be an alternative for the well-defined Ru-based initiators which rules out the need of installation of complex ancillary ligands like NHC or O-Ligand in the coordination sphere or the need of activation with diazo compounds in the search for novel active catalytic species. Further study on the catalytic polymerization activity of Ru(p-cymene)H2PCy3 compared to the Ru(p-cymene)HClPCy3 system revealed that chloride ligand was also crucial to the hydride containing mononuclear ruthenium system, which contains easily dissociated ligand p-cymene and large phosphine ligand that stabilizes the metal complex. And the possible mechanism for the reaction was proposed.

Polymerization of ɛ-caprolactone by lanthanide trisborohydrides and crystal structure of [Ce(BH4)2(THF)5][Ce(BH4)4(THF)2

Complexes of lanthanide trisborohydrides, formally Ln(BH4)3(THF)n (Ln=La, Ce, Sm, Yb), were synthesized and their catalytic activity for polymerization of ɛ-caprolactone was studied. All the complexes can catalyze this polymerization. It was found that the catalytic activities decreased in the order of La>Ce>Sm>Yb. The crystal structure of cerium trisborohydride was determined for the first time by single crystal X-ray diffraction analysis. It is an ionic pair complex of [Ce(BH4)2(THF)5][Ce(BH4)4(THF)2]. The cationic part involves two η3-BH4 ligands, while the anionic part involves two η3-BH4 groups and two η2-BH4 groups.

Novel antimicrobial polyethylene composites prepared by metallocenic in situ polymerization with TiO2‐based nanoparticles

AbstractPolyethylene (PE) composites with titanium oxide (TiO2) nanoparticles were produced via in situ polymerization representing a novel route to obtain antimicrobial polymeric materials. The TiO2 nanoparticles synthesized by the sol–gel method were used either as‐synthesized or modified organically with hexadecyltrimethoxysilane (Mod‐TiO2). These particles were added, together with the catalytic system (formed by a metallocenic catalyst and methylaluminoxane as cocatalyst), directly to the reactor, yielding in situ PE composites with 2 and 8 wt % content of nanofiller. The catalytic polymerization activity presented a slight decrease with the incorporation of the TiO2 and Mod‐TiO2 nanoparticles compared to polymerization without filler. Regarding the properties of the composites, crystallinity increased slightly when the different nanofillers were added, and the elastic modulus increased around 15% compared to neat PE. PE/TiO2 nanocomposites containing 8 wt % of TiO2 exposed to UVA irradiations presented antimicrobial activity against Escherichia coli. The PE/Mod‐TiO2 nanocomposite with 8 wt % filler killed 99.99% of E. coli, regardless of light and time irradiation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Polymerization of n-butyl methylacrylate using bis(β- ketoamino)nickel(II)/MAO catalytic systems

AbstractThe polymerizations of n-butyl methylacrylate (nBMA) were carried out using bis(β-ketoamino)nickel(II) complexes (Ni[CH3C(O)CHC(NR)CH3]2: R = phenyl, 1; R = naphthyl, 2) in combination with methylaluminoxane (MAO) in toluene. The effect of parameters such as polymerization temperature, Al/Ni molar ratios, polymerization time, and monomer concentration, on catalytic polymerization activity and polymer molecular weights, were examined in detail. Both of the nickel(II) catalytic systems exhibited moderate activity, and produced P(nBMA) with high molecular weight and relatively broad molecular weight distribution (Mw/Mn=2.0~3.0. The obtained polymer has been characterized by means of FTIR, 1H NMR, 13C NMR, DSC, and WAXD technique and was confirmed to be syndio-rich stereospecific P(nBMA).

Bis(μ-carboxylato)dienerhodium(I) Complexes - Synthesis, Characterization and Catalytic Activity

Dinuclear rhodium(I) η2:η2-cycloocta-1,5-diene (series a) and η2:η2-norborna-2,5-diene (series b) complexes with μ-RCOO- ligands, where R is linear C21H43 (complexes 1a, 1b), CH2CMe3 (2a, 2b), 1-adamantyl (3a, 3b) and benzyl (4a, 4b), have been prepared and characterized by spectroscopic methods. Structures of complexes 2b, 3a and 4a were determined by X-ray diffraction analysis. Complexes prepared show low to moderate catalytic activity in polymerization of phenylacetylene in THF giving high-cis-transoid polymers, but they show only oligomerization activity in dichloromethane.

Synthesis, molecular structure, and catalytic activity of borohydride complexes [(Me3Si)2NC(NPri)2]2Nd(BH4)2Li(thf)2 and [(Me3Si)2NC(NPri)2]2Sm(BH4)2Li(thf)2

The reactions of lanthanide tris(borohydrides) Ln(BH4)3(thf)3 (Ln = Sm or Nd) with 2 equiv. of lithium N,N′-diisopropyl-N′-bis(trimethylsilyl)guanidinate in toluene produced the [(Me3Si)2NC(NPri)2]Ln(BH4)2Li(thf)2 complexes (Ln = Sm or Nd), which were isolated in 57 and 42% yields, respectively, by recrystallization from hexane. X-ray diffraction experiments and NMR and IR spectroscopic studies demonstrated that the reactions afford monomeric ate complexes, in which the lanthanide and lithium atoms are linked to each other by two bridging borohydride groups. The complexes exhibit catalytic activity in polymerization of methyl methacrylate.

Syndiotactic-enriched propylene–styrene copolymers using fluorenyl-based half-titanocene catalysts

The constrained geometry complexes {3,6- t Bu 2C 13H 6SiMe 2N t Bu}TiCl 2 (X = Cl, 1; Me, 2), in combination with MAO or borane activators, have been investigated in the copolymerization of propylene with styrene at 25–60 °C, 1–5 atm. Both systems were found to give styrene–propylene (PP–PS) copolymers with up to 24 mol% of styrene incorporated and moderate molecular weights ( M w = 14,000–88,000; M w/ M n = 1.58–2.32). Addition of some ethylene to the styrene–propylene feed improves the catalytic polymerization activity. The PP–PS copolymers feature a syndiotactic-enriched polypropylene microstructure ( r > 92%), with randomly distributed single styrene and/or short polystyrene units.

Palladium and nickel complexes of (P,N)-ligands based on quinolines: Catalytic activity for polymerization and oligomerization

Four (P,N)-ligands ( 1– 4) with different steric and electronic properties were synthesized. They were used to prepare the monocationic palladium complexes [Pd(P,N)(CH 3)(NCCH 3)](PF 6) ( 9– 12). The structures of the newly prepared ligand 3 and the neutral palladium complex [Pd(P,N)(CH 3)Cl] ( 10) were analysed by X-ray. The catalytic activity of the palladium complexes toward the copolymerization of styrene and ethylene with CO was low or non-existent. The nickel complexes [Ni(P,N)(1-naphthyl)Cl] ( 13– 16), modified with the ligands 1– 4, were prepared and their catalytic activity toward ethylene oligomerization was studied. They showed high activity at ambient temperature and low ethylene pressure (1–12 bar) in the presence of MAO.