Active Polymerization Catalysts Research Articles

Synthesis, structure, and butadiene polymerization behavior of alkylphosphine cobalt(II) complexes

The synthesis, characterization and behavior in polymerization of 1,3-butadiene of some cobalt(II) phosphine complexes (CoCl 2(PEt 3) 2, CoCl 2(P n Pr 3) 2, CoCl 2(PCy 2H) 2, CoCl 2(P t Bu 2H) 2, CoCl 2(P t Bu 2Me) 2, CoCl 2(PCyp 3) 2, CoCl 2(PCy 3) 2; Et = ethyl, n Pr = normal-propyl, Cy = cyclohexyl, t Bu = tert-butyl, Cyp = cyclopentyl) are described. The X-ray diffraction studies of CoCl 2(PCy 3) 2 and CoCl 2(PCy 2H) 2 are reported. Treatment of these complexes with methylaluminoxane (MAO) leads to highly active butadiene polymerization catalysts; polymers having different microstructure have been obtained depending on the type of phosphine ligand bonded to the cobalt atom. An interpretation for this particular behavior, based on the 1,3-dienes polymerization mechanism previously proposed, is given.

Highly Active Yttrium and Lanthanide Catalysts for Polymerization of Isobutene

AbstractSummary: Highly active catalysts for isobutene polymerization were obtained by mixing silica with yttrium or lanthanide chloride salts. Solid catalysts were investigated using transmission electron microscopy and Raman spectroscopy. Both Lewis and Brönsted acid sites were detected on the surface. Polymers of low and medium molecular weight were prepared and their unsaturated chain ends were fully investigated by one‐ and two‐dimensional NMR analyses.13C NMR spectrum of a low‐molecular‐weight polyisobutene (high‐field resonance region).image13C NMR spectrum of a low‐molecular‐weight polyisobutene (high‐field resonance region).

A Remarkably Facile Zirconium(IV) → Aluminum(III) β-Diketiminate Transmetalation That Also Results in a More Active Olefin Polymerization Catalyst upon Activation

(R-IAN)2ZrX2 complexes, where X = NMe2, Cl, have recently emerged as effective olefin polymerization precatalysts bearing chiral ligands formally of the β-diketimine class. An attempt to exchange dimethylamido ligands for alkyl (methyl) using the Jordan protocol resulted in a surprisingly facile transmetalation of the bidentate Me-IAN ligands from zirconium(IV) to aluminum(III). An initial study of the process and the finding that the (R-IAN)AlMe2 complexes that result are more potent precatalysts themselves provide a case study within the rapidly growing area of catalysis based on β-diketiminate metal complexes.

Nickel(II) Isocyanide Complexes as Ethylene Polymerization Catalysts

Isocyanide complexes of nickel, NiBr2(CNAr)2, are found to be active catalysts for polymerization of ethylene in the presence of methylaluminoxane (MAO). The catalytic activity and properties of polyethylene formed vary with substituents on the aryl group, in particular, at the 2- or 2,6-positions. The nickel complexes having 2,6-diphenylphenylisocyanide and its analogues are catalysts showing moderate activity and giving high molecular weight polyethylene (Mv > 106), whereas those bearing 2-phenylphenylisocyanide and its analogues give polyethylene with Mw = 103−104.

Highly active and stereoselective olefin polymerization catalysts generated by the transfer‐epimetallation of olefins or acetylenes with dialkyltitanium(IV) complexes: three‐membered metallocycles as active catalyst sites‡

AbstractEfficient transfer‐epimetallations of simple olefins and acetylenes by R2TiL2 reagents (R = Bun, But; L = X) are readily achieved in THF at −78°C to generate titanacyclopropa(e)ne intermediates, readily capable of inserting various unsaturated addends (olefin, acetylene, nitrile). Analogous epimetallations conducted in hydrocarbons lead to the isotactic stereoselective polymerization of 1‐alkenes and the cyclotrimerization of acetylenes. In place of the widely accepted Arlman‐Cossee model for the active catalytic site, namely a Ti‐C bond on the TiCl3 crystal lattice, the 2‐substituted‐1‐halotitanacyclopropyl cation formed in hydrocarbon media is proposed as the active site for stereoselective olefin polymerization.

The Cs-Symmetric Aminoboranediyl-Bridged Zirconocene Dichloride [(η-9-C13H8)- BN(iPr)2(η-C5H4)]ZrCl2: Its Synthesis, Structure, and Behavior as an Olefin Polymerization Catalyst

The sequential reaction of 9-fluorenyllithium and CpNa with (iPr)2NBCl2 followed by the sequential treatment with LDA and ZrCl4 afforded [(η5-C13H8)BN(iPr)2(η5-C5H4)ZrCl2 (2e). The structure of 2e was determined by X-ray diffraction, which shows that the molecule has Cs symmetry. On activation by excess methylaluminoxane (MAO) 2e was converted to an active catalyst for polymerization of ethylene and propylene. The polypropylene is syndiotactic (81% rr triads).

Cp 2TiCl 2] as polymerization catalyst in aqueous medium: polymerization of styrene in water

The contrary to the general idea, an early transition metal organometallic compound, [Cp 2TiCl 2] has been found to be active catalyst for aqueous medium polymerization of styrene.

Synthesis of the new, weakly coordinating anions [RB(C6F5)3]−(R = CH2Me, CHMe2, CH2CMe3); utilization of [HNMe2Ph][Me3CCH2B(C6F5)3] to activate zirconocene catalysts for propylene polymerization

The compound [HNMe2Ph][NpB(C6F5)3](Np =(CH3)3CCH2) reacts with dimethylzirconocenes to give active propylene polymerization catalysts which are significantly more active and give higher molecular weight polypropylene than do the catalysts obtained using B(C6F5)3; the [NpB(C6F5)3]- anion is for steric reasons more weakly coordinating than is [MeB(C6F5)3]-.

Quinolyl-functionalised Cp–chromium polymerisation catalysts: synthesis and crystal structures of alkylation products

The quinolyl-functionalised Cp–chromium(III) complexes 1 and 2, which serve as precursors for highly active olefin polymerisation catalysts, were alkylated with benzylmagnesium chloride. From these reactions, the new metal complexes 4, 5 and 6 were obtained and structurally characterised. The expected alkylchromium compound 4 is formed together with complex 5, where the nucleophile replaced a hydrogen atom at the quinoline substituent. The dinuclear complex 6 is formed by nucleophile addition, rearrangement and dimerisation.

Chromium(II) and chromium(III) complexes supported by tris(2-pyridylmethyl)amine: synthesis, structures, and reactivity.

This report describes the synthesis, structural characterization, and polymerization behavior of a series of chromium(II) and chromium(III) complexes ligated by tris(2-pyridylmethyl)amine (TPA), including chromium(III) organometallic derivatives. For instance, the combination of TPA with CrCl(2) yields monomeric (TPA)CrCl(2) (1). A similar reaction of CrCl(2) with TPA, followed by chloride abstraction with NaBPh(4) or NaBAr(F)(4) (Ar(F) = 3,5-(CF(3))(2)C(6)H(3)), provides the weakly associated cationic dimers [(TPA)CrCl](2)[BPh(4)](2) (2A) and [(TPA)CrCl](2)[BAr(F)(4)](2) (2B), respectively. X-ray crystallographic analysis reveals that each chromium(II) center in 1, 2A, and 2B is a tetragonally elongated octahedron; such Jahn-Teller distortions are consistent with the observed high spin (S = 2) electronic configurations for these chromium(II) complexes. Likewise, reaction of CrCl(3)(THF)(3) with TPA, followed by anion metathesis with NaBPh(4) or NaBAr(F)(4), yields the monomeric, cationic chromium(III) complexes [(TPA)CrCl(2)][BPh(4)] (4A) and [(TPA)CrCl(2)][BAr(F)(4)] (4B), respectively. Treatment of 4A with methyl and phenyl Grignard reagents produces the cationic chromium(III) organometallic derivatives [(TPA)Cr(CH(3))(2)][BPh(4)] (5) and [(TPA)CrPh(2)][BPh(4)] (6), respectively. Similar reactions of 4A with organolithium reagents leads to intractable solids, presumably due to overreduction of the chromium(III) center. X-ray crystallographic analysis of 4A, 5, and 6 confirms that each possesses a largely undistorted octahedral chromium center, consistent with the observed S = (3)/(2) electronic ground states. Compounds 1, 2A, 2B, 4A, 4B, 5, and 6 are all active polymerization catalysts in the presence of methylalumoxane, producing low to moderate molecular weight high-density polyethylene.

Halogen-Substituted 2,6-Bis(imino)pyridyl Iron and Cobalt Complexes: Highly Active Catalysts for Polymerization and Oligomerization of Ethylene

A series of halogen-substituted 2,6-bis(imino)pyridyl ligands and their iron and cobalt complexes [｛2,6-(2,6-X1X2C6H3NdCCH3)2C5H3N＝MCl2] (X1 ＝ X2 ) Br, M ＝ Fe (1), Co (2); X1＝ X2 ＝ Cl, M ＝ Fe (3), Co (4); X1 ＝ Cl, X2 ＝ H, M ＝ Fe (5), Co (6); X1 ＝ Br, X2 ＝ H, M ＝ Fe(7), Co (8); X1＝ I, X2 ＝ H, M ) Fe (9), Co (10)) and [M｛2,6-(2,6-X1X2C6H3NdCCH3)2C5H3N?2｝]2+- [MCl4]2- (X1 ) F, X2 ) H, M ) Fe (11)) have been synthesized. The molecular structures of complexes 1, 8, 9, 10, and 11 were determined by X-ray diffraction. Crystallographic analyses indicate that 1, 8, 9, and 10 are five-coordinate complexes, while 11 is an ion-pair complex with one six-coordinate iron center and one four-coordinate iron center. These metal coordinative complexes, activated by modified methylaluminoxane (MMAO), lead to highly active ethylene polymerization and/or oligomerization catalysts. The catalyst productivity and product properties crucially depended on the metal center and the halogen substituents on the aryl rings. The catalyst productivities are in the range of (0-73.0) _ 106 g/mol of catah. The species 11, having ion-pair structure, is inactive. In particular, the product molar masses were changed from high molar mass (Mw of 377 000) to low molar mass oligomers by varying the halogen substituents. NMR and thermal analyses reveal the polymer is highly linear. The oligomer products follow a Schulz-Flory distribution with high selectivity for linear R-olefins. The effects of reaction condition on the polymerization and oligomerization have also been studied.

Preparation of chelate bis(imine)nickel allyl systems by reaction of their corresponding butadiene complexes with electrophiles

The chelate 1,2-bis(imine)nickel(butadiene) complex 4a (chelate ligand derived from condensation of biacetyl with 2,6-diisopropylaniline) adds the strong Lewis acid B(C 6F 5) 3 at the terminal carbon atom of the butadiene ligand to yield the dipolar substituted π-allyl-type betaine complex (lig)Ni[η 3-C 3H 4-CH 2B(C 6F 5) 3] ( Z- 6a). At 90 °C the kinetically formed product equilibrated with its E- 6a isomer. Similarly, 4a adds the boron Lewis acid (pyrrolyl)B(C 6F 5) 2 to yield the corresponding neutral dipolar π-allyl betaine complex Z- 7a, that slowly equilibrated with E- 7a over several hours at ambient temperature. Protonation of the butadiene ligand of complex 4a was achieved by treatment with the neutral Brønsted acid (2H-pyrrol)B(C 6F 5) 3 to yield the [(lig)Ni(η 3-crotyl) +][(pyrrolyl)B(C 6F 5) 3 −] salt 9a ( Z-/ E- 9a ratio=90:10 upon preparation). At 298 K this salt rearranged to a 5:95 mixture of Z- 9a/ E- 9a with a Gibbs activation energy of Δ G ‡ (298 K)=22.3±0.2 kcal mol −1. Complex 4a added [Ph 3C +] to the butadiene ligand to yield the salt [(lig)Ni(η 3-C 3H 4-CH 2CPh 3) +][B(C 6F 5) 4 −] ( Z- 12a), that proved isomerically stable under the applied reaction conditions. Similar reactions were carried out starting from the acenaphthylene 1,2-dione derived chelate bis(imine)Ni(butadiene) complex 4b. The systems 6, 7, 9 and 12 were found to be active ethene polymerization catalysts in the presence of Al( i-Bu) 3.

Design of highly active iron-based catalysts for atom transfer radical polymerization: tridentate salicylaldiminato ligands affording near ideal Nernstian behavior.

Iron(II) complexes bearing monoanionic tridentate salicyladiminato ligands are shown to be highly efficient catalysts for atom transfer radical polymerization (ATRP). Polymerization rates for styrene are among the highest reported for iron-mediated ATRP in nonpolar media, correlating well with E1/2 potentials and DeltaEp values for the complexes. The rigidity of the tridentate ligands, combined with ample space around the metal center to accommodate a halogen atom, we believe to be an important factor in the efficient ATRP behavior of these systems.

Siloxyaluminum Alkyl Cations: Syntheses, Structures, and Reactions Related to Activation of Zirconocene Catalysts on Silica Gel Surfaces

Binuclear siloxyaluminum methyl complexes of the type Me2Al(μ-OSiR3)2AlMe2 react with protonated N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate, with release of CH4, to form the dimethylaniline (DMA)-stabilized siloxyaluminum methyl cations Me2Al(μ-OSiR3)2AlMe(NMe2(C6H5)+. These cations abstract a Cl- ligand from (C5H5)2ZrCl2, to give the dinuclear cation {(C5H5)2ZrCl}2(μ-Cl)+, and a CH3- ligand from (C5H5)2Zr(CH3)2, to give by way of the DMA-stabilized cation (C5H5)2Zr(CH3)NMe2(C6H5)+ the CH-activation product (C5H5)2ZrCH2NMe(C6H5)+; reaction with Me2Si(ind)2ZrMe2 in toluene solution yields a moderately active catalyst for ethene polymerization. This reactivity of siloxyaluminum methyl cations is qualitatively similar to, although substantially lower than, that of a silica gel surface treated with trimethylaluminum and a cationizing agent.

Role of B(C6F5)3 in catalyst activation, anion formation, and as C6F5 transfer agent

Abstract The versatile reactivity of B(C6F5)3 in alkene polymerization reactions is summarized. Adduct formation with basic anions such as CN– and NH2– gives extremely weakly co- ordinating diborates, which are the basis of some of the most active polymerization catalysts known to date. By contrast, the reaction of B(C6F5)3 with zirconium half-sandwich complexes leads to extensive C6F5 transfer, including the surprising formation of borole-bridged triple decker complexes. Main group alkyls undergo such C6F5 exchange reactions very readily unless donor ligands are present. Borate salts of new three-coordinate zinc alkyl cations proved to be highly effective catalysts for the ring-opening polymerization of epoxides and lactones.

Highly efficient ethylene polymerisation by scandium alkyls supported by neutral fac-kappa3 coordinated N3 donor ligands.

Reaction of [M(CH2SiMe3)3(THF)2] (M = Sc or Y) with the neutral fac-kappa3 N3 donor ligands (L) Me3[9]aneN3 or HC(Me2pz)3 gave the corresponding trialkyls [M(L)(CH2SiMe3)3]; activation of the scandium congeners with B(C6F5)3 in the presence of ethylene afforded highly active polymerisation catalysts (Me3[9]aneN3 = 1,4,7-trimethyltriazacyclononane).

Group IV complexes of an amine bis(phenolate) ligand featuring a THF sidearm donor: from highly active to living polymerization catalysts of 1-hexene

A new amine bis(phenolate) ligand bearing a THF donor on a sidearm and several dialkyl complexes of the group IV triad are introduced. The crystal structures of a zirconium dibenzyl complex and a titanium dibenzyl complex were solved, and revealed a strong binding of the oxygen donor of the THF group to the metal center. Upon activation with tris(pentafluorophenyl)borane the zirconium and the hafnium dibenzyl complexes lead to highly active 1-hexene polymerization catalysts. In comparison, titanium complexes (a dibenzyl complex and a dimethyl complex) lead to slower but living polymerization of 1-hexene at room temperature. Polymerization of neat 1-hexene under high dilution conditions was found to be living for an exceptionally long time of 6 days, leading to poly(1-hexene) of M w=816 000 and PDI=1.09. A block copolymerization of 1-hexene and 1-octene at room temperature could be obtained using the titanium catalysts.

Structural characterization of Group 4 transition metal halide bis-Arduengo carbene complexes MCl 4L 2: : X-ray crystal structure analyses and DFT calculations

The Arduengo carbenes 1,3-diisopropyl-, 1-methyl-3-(1-methylpropyl)-, and 1-methyl-3-(2,4,6-trimethylbenzyl)imidazol-2-ylidene ( 3a– c) were reacted with MCl 4(thf) 2 (M=Zr, Hf) to yield the respective trans-(imidazol-2-ylidene)MCl 4 complexes 4a– c (M=Zr) and 5a (M=Hf), respectively. These four Arduengo carbene-Group 4 metal halide complexes were characterized by X-ray diffraction. The pairs of carbene ligands are trans-positioned in a pseudo-octahedral coordination geometry at the Group 4 metals, and adopt a conformational orientation in the solid state where the two five-membered heterocycles are arranged coplanar and bisecting the ClMCl angle. DFT calculations have shown that the Arduengo carbenes serve as pure σ-donor ligands in these complexes and that the preferred conformational ligand orientation is based on steric reasons. The complexes 4a– c form moderately active ethene polymerization catalysts when activated with a large excess of methylalumoxane in toluene.

Propylene polymerization with a bisiminepyridine iron complex: activation with Ph 3C [B(C 6F 5) 4] and AlR 3; iron hydride species in the catalytic cycle

In this work, the complex 2,6-bis [1-(2-isopropyl-6-methylphenylimino)ethyl]-pyridineiron(II)dichloride was used for propylene polymerization. Activation with Ph 3C [B(C 6F 5) 4] and subsequent treatment with triisobutylaluminium or triethylaluminium generated a very active polymerization catalyst for propylene. The kinetics of this polymerization reaction were investigated with mass-flowmeters. Further we show propagation-time-profiles of this reaction. Depending on the nature of the aluminiumalkyl we are able to determine different aliphatic endgroups in the polymer using 13 C NMR spectroscopy. Addition of hydrogen to the polymerization leads to higher activities and allows us to formulate a complete catalytic reaction cycle containing an iron hydride species. This cycle comprises one starting cycle and two propagation cycles which can be controlled with the aluminiumtrialkyl-propylene ratio.

Organoborane-Modified Silica Supports for Olefin Polymerization: Soluble Models for Metallocene Catalyst Deactivation

Treatment of silsesquioxane 1 with 3.3 equiv of the reactive organoboranes 2 [(C6F5)2BX; X = H or Cl] provides the novel, trifunctional organoborane 3, which was characterized by spectroscopic means and single-crystal X-ray crystallography. Compound 3 is an effective cocatalyst for ethylene polymerization in combination with Cp2ZrMe2 but only when these two compounds are combined in situ, in the presence of monomer, suggesting limited stability of the putative ion-pair derived from these compounds. Reaction of 3 with Cp2ZrMe2 in toluene solution leads to formation of MeB(C6F5)2- and Cp2Zr-functionalized silsesquioxane 5 at room temperature. Monitoring of this reaction by NMR spectroscopy at low temperatures indicates that the only ion-pair present is [Cp2ZrMe][Me2B(C6F5)2] (4), which results from reaction of Cp2ZrMe2 with the byproduct MeB(C6F5)2. Formation of 4 is reversible under these conditions, while production of 5 (from 3 and Cp2ZrMe2) is not; the latter process occurs at a rate that exceeds that observed for independent decomposition of 4 to form Me2B(C6F5) and Cp2Zr(C6F5)Me. These studies suggest that the active polymerization catalyst generated in situ from 3 and Cp2ZrMe2 is probably ion-pair 4.