Cp2Zr Cl Research Articles

Semiempirical study of metallocenes adsorption on β-MgCl 2

This work analyzes the adsorption of four metallocenes with different symmetry on two planes of β-MgCl 2: the (100) and the (110). The selected metallocenes are Cp 2ZrCl 2, Ind 2ZrCl 2, EtInd 2ZrCl 2 and Me 2SiInd 2ZrCl 2. The results of the calculations allow us to speculate that the chiral ansa metallocenes bridged with C 2H 4 could have chemical interaction with certain faces of the MgCl 2 surface during the stage of adsorption and subsequent precursors treatment, while the interaction of the others with the surface generates stable species depending on the surface geometry.

Sterisch überladene indenylkomplexe des zirconiums und hafniums

The reaction of zirconocene dichloride, Cp 2ZrCl 2, and bis(indenyl) metal dichloride, Ind 2MCl 2 (M = Zr, Hf), with one and two equivalents, respectively, of indenyl or fluorenyl lithium leads to sterically crowded complexes with three or four potential π-ligands ( 1: Cp 2Zr(Ind)Cl; 2: Cp 2Zr(Ind) 2; 3: Ind 3ZrCl; 4: Ind 3HfCl; 5: Ind 2Zr(Flu)Cl). Compound 4 was characterized by an X-ray structure analysis.

Styrene polymerization using titanium- n-butoxide-sterically hindered aryloxy derivative of trimethylaluminum catalyst system

Styrene was polymerized using bis(2,6-di- tert-butyl,4-methylphenoxy)methylaluminum as cocatalyst and titanium-n-butoxide, titanium phenoxide and Cp 2ZrCl 2 as catalysts. Both conversion and % of acetone insoluble fraction of poly(styrene) increased with an increase in polymerization temperature and time for titanium-n-butoxide-bis(2,6-tert butyl, 4-methylphenoxy)methylaluminum catalyst-initiated polymerization. Conversion was invariant with a change in Al Ti ratio for the above catalyst-initiated styrene polymerization. Poly(styrene) produced was found to be atactic in nature with mm, mr and rr triad concentrations 33.8, 51.9 and 14.2%, respectively. Poly(styrene) produced was characterized by 13C NMR, DSC, solubility in boiling acetone and intrinsic viscosity measurements.

Catalytic dehydrocoupling of PhSiH 3 with bimetallic Ti and Zr complexes

Bimetallic titanium and zirconium complexes with bridges (X) between Cp ligands were compared to Cp 2MCl 2 as catalysts in the presence of nBuLi for the dehydrocoupling of PhSiH 3 to polyphenylsilane. The monobridged bimetallic complexes developed were of the composition [μ-X(C 5H 4) 2][CpMCl 2] 2 with XMe 2Si (MTi, Zr), Me 2SiCH 2SiMe 2 (MTi) and Me 2SiCH 2CH 2SiMe 2 (MTi, Zr). The dibridged bimetallic complexes examined were of the type [μ,μ-(Me 2Si) 2(C 5H 3) 2][Cp′TiCl 2] 2 (Cp′  Cp, trans isomer, Cp′ = Cp *, trans and cis isomers). There was not a significant difference in the molecular weight of the polysilane produced from Cp 2TiCl 2 and the bimetallic titanium complexes after 48 h of reaction. However, the polysilane which was generated from the bimetallic complex [μ-(Me 2Si)(C 5H 4) 2][CpZrCl 2] 2 was approximately twice the molecular weight compared to that obtained from Cp 2ZrCl 2. The structure of the bimetallic complex [μ-(Me 2SiCH 2CH 2SiMe 2)(C 5H 4) 2][CpZrCl 2] 2 was determined by X-ray diffraction (monoclinic, P2 1/ n, a = 8.7297(3) A ̊ , b = 6.7890(2) A ̊ , c = 24.9343(7) A ̊ , β = 93.7850(10)°, Z = 2).

Synthesis of novel heterocycles by the reaction of N,C-dilithio-2-allylpyrrole with electrophiles

N,C. dilithio-2-allylpyrtole ( 1) in THF reacts selectively with various element halides to give Z-isomers, and in the case of element dihalides (Me 2SiCl 2, Me 2SnCl 2, Cp 2ZrCl 2) or SiCl 4 to give new heterobicycles [E  Si ( 7), Sn ( 8), Zr ( 12)] or the spirosilane 6. Treatment of 1 with triethoxyborane gives the heterobicyclic borate 9 which reacts with Me 3SiCl to give the heterobicyclic ethoxyborane 10. The synthetic potiential of 8 is shown by its transformation to the heterobicyclic ethylborane 11. All compounds were characterized by multinuclear magnetic resonance, including the application of modified (Hahn-echo extended) polarization transfer pulse sequences for measurement of nJ ( 29Si, 15N), 1 J( 119Sn, 15N) and 2D 13C/ 1H heteronuclear shift correlations for the determination of signs of coupling constants nJ ( 119Sn, 13C) and n+1J ( 119Sn, 1H).

Reactions of Group IV Metallocene Dichlorides with Modified Silica Gel Surfaces

Reactions of bis(cyclopentadienyl)titanium dichloride, bis(cyclopentadienyl)zirconium dichloride, and bis(cyclopentadienyl)hafnium dichloride with premodified silica gel surfaces were studied. The silica gel surface was pretreated to selectively eliminate nonhydrogen bonded silanols, hydrogen bonded silanols, or both before reaction. By study of the metallocene reactions with these silicas and unmodified silica gel, it was found that the metallocenes react predominantly with nonhydrogen bonded silanols. Although none of the metallocenes are very reactive with silica as compared to titanium tetrachloride, reactivity increases in the order Cp 2TiCl 2< Cp 2ZrCl 2< Cp 2HfCl 2.

Kinetics of olefin polymerization catalysed by various zirconocene/aluminoxane systems at low Al/Zr ratios

Ethylene, propylene and 1-butene polymerization kinetics have been investigated in the presence of 16 zirconocene and ethylalumoxane derivatives with various molecular masses and a molar ratio of Al/Zr = 23–26. It was found that zirconocene activity in combination with ethylalumoxanes with molecular weight MW = 880 (an oligomer with -[OAl(C 2H 5)]- unit number equal to 10) increases in series: Cp(Acac) 2ZrCl < (Fulv) 2Cp 2Zr 2Cl 2 < Cp 2ZrMe 2 < (Fulv) 2Cp 2Zr 2(O)Cl 2 < (Ind) 2ZrCl 2 < ( t-Bu 2Cp) 2ZrCl 2 < Cp 2ZrCl 2 < ( t-BuCp) 2ZrCl 2 < (MeCp) 2ZrCl 2 < (i-PrCp) 2ZrCl 2, where Fulv - fulvalene. With methylalumoxane (MW = 1930, (-[OAl(CH 3)]- unit number 31) the following series of zirconocene activity was established: (MeCp) 2ZrCl 2 < (EtCp) 2ZrCl 2 < (PrCp) 2ZrCl 2 < (BuCp 2ZrCl 2 < (i-PrCp) 2ZrCl 2 < (Cyclo-HexCp) 2ZrCl 2.

A comparison of ( n-butCp) 2ZrCl 2 and other simple metallocenes with bridged Et(Ind) 2ZrCl 2 and Me 2Si(Ind) 2ZrCl 2 catalysts in ethene/propene copolymerization

A study was made of the behaviour of four non-bridged metallocenes, in particular ( n-butCp) 2ZrCl 2 in ethene/propene (E/P) copolymerization, and the findings were compared with those for bridged Et(Ind) 2ZrCl 2 and Me 2Si(Ind) 2ZrCl 2 catalysts. Methylaluminoxane was used as a cocatalyst in all polymerizations. The influence of the catalyst structure on the propene content, the reactivity ratios, the comonomer distribution in the polymer backbone, molar mass, molar mass distribution, density and melting point of the synthesized material were of interest. The bridged metallocenes were found to be more active catalysts for propene incorporation than the non-bridged ones. The comonomer distributions of all polymers except those obtained with an Ind 2ZrCl 2 catalyst were random. At the same propene molar content in the copolymer, densities and melting points were lower for materials synthesized with non-bridged catalysts than for materials synthesized with bridged catalysts due to the lack of chirality in the catalysts of C 2v symmetry. Except Cp 2ZrCl 2, the non-bridged metallocenes produced higher molar mass copolymers than their bridged analogues. Polydispersities of the materials varied with the catalyst and no uniformity of behaviour was detected for the simple metallocenes.

Preparation of 1,2,3-trisubstituted cyclopentadienes and tetrahydroindene derivatives from zirconacyclopentenes

1,2,3-Trisubstituted cyclopentadienes and tetrahydroindene derivatives were prepared by a one-step reaction from zirconacyclopentene complexes, which are easily prepared from alkynes and EtMgBr (or ethylene) and Cp 2ZrCl 2. Reaction of zirconacyclopentenes with phthaloyl chlorides afforded intramolecular Michael addition reaction products. The structure of one of the products was determined by X-ray study.

Synthesis and structural characterisation of the novel metallasiloxane compound [Cp 2∗ZrOSiPh 2OLiOH] 2

The reactions between Cp 2ZrCl 2 or Cp 2 ∗ZrCl 2 with in situ generated Ph 2Si(OLi) 2 gave unexpected dimeric cyclozirconasiloxane products incorporating LiOH within the chelate-bridging unit OSiPh 2OLi(OH). The crystal structure of [Cp 2 ∗ ZrOSiPh 2OLiOH] 2 is reported and the origin of the LiOH discussed.

Ligand effects on olefin polymerizations with multinuclear zirconocene catalysts having dimethylsilylferrocene as a cyclopentadienyl substituent

AbstractOlefin polymerizations were conducted with novel multimetallic zirconocene catalyst systems: RCpCpZrCl2 (1) (R = dimethylsilylferrocene; Cp = cyclopentadienyl) and (RCp)2ZrCl2 (2) in combination with methylaluminoxane or tetrakis(pentafluorophenyl) borates. In ethylene polymerization, the maximum catalyst activity was observed at a lower temperature (30–45°C) when using complex 1 or 2, compared with Cp2ZrCl2. It was also revealed that complex 1 is a more effective catalyst than Cp2ZrCl2 for copolymerization of ethylene and propene.

Formation of novel P- and As-functionalized ligands by insertion reactions into the ZrE bond of ( η5−C 5H4R) 2ZrCl{ E( SiMe3) 2} (R = Me, E = P, As; R = H, E = P)

Cp′ 2ZrCl{P(SiMe 3) 2} (Cp′ = η 5−C 5H 4Me) undergoes insertion of PhNC into the ZrP bond, yielding Cp′ 2ZrCl{ η 2-N(Ph)CP(SiMe 3) 2} ( 1). Cp 2ZrCl{P(SiMe 3) 2} (Cp = η 5−C 5H 5) and Cp′ 2ZrCl{As(SiMe 3) 2} insert Pr iNCNPr i into the Zror ZrAs bond with the formation of ▪ ( 2) and ▪ ( 3). 1–3 were characterized spectroscopically, and a crystal structure determination carried out on 3 shows an η 2-bonding mode of the NPr iC {E(SiMe 3) 2} NPr i ligand.

XPS study of metallocene based catalysts for the polymerization of ethylene

X-ray photoelectron spectroscopy (XPS) has been applied to the study of a series of metallocene catalysts, containing Zr, Ti or Hf, for the polymerization of ethylene. Surface atomic compositions, binding energies and valence band (VB) spectra have been measured. Surface compositions were found to be more or less similar to the expected values on the basis of molecular structure depending on the stability of compounds vs. air contact. XPS analyses after air exposure showed a marked tendency of metal-Cl bonds to be substituted by metal-O bonds. Binding energy of zirconium was found to be rather sensitive on the overall electron-attractive effect of ligands, with the following energy scale: ZrCl 4 > Cp 2ZrF 2 > CpZrCl 3 > Cp 2ZrCl 2 = (Cp 2ZrCl) 2O > Cp 2Zr(NET 2) 2. A relationship was found with catalytic activity, which seems to be favoured by a low binding energy value of Zr. VB spectra have been discussed, showing peculiar features depending on the molecular structure.

Hydrooligomerization of cycloolefins -a view of the microstructure of polynorbornene

Hydrooligomerizations of norbornene were carried out using C 2, C s and C 2 v symmetric zirconocenes with methylaluminoxane as catalysts. The structures of the hydrodimers and -trimers were investigated and correlated to the symmetry of the metallocene. The polymerization of norbornene is shown to proceed by cis-exo insertion. The mechanisms of polymerization and stereocontrol are closely related to the ones observed in the polymerization of α-olefins. Thus the C 2 symmetric metallocene features erythrodiisotactic structures, while erythrodisyndiotactic products are observed in case of the C s symmetric one. This is caused by enantiomorphic site control, while stereospecificity in the hydrooligomerization using Cp 2ZrCl 2 MAO is determined by chain end control mechanism.

Synthesis of 2-(diphenylphosphino)phenolato and 2-(diphenylphosphinomethyl)-4-methylphenolato complexes of titanium and zirconium. X-ray characterization of [( η5-C 5H5) 2ZrCl(OC 6H4PPh2] and [( η5-C 5H 5) 2 Zr(OC 6H 4PPh 2) 2

Complexes [(C 5H 5) 2MCl 2] (MTi, Zr) react with the 2-(diphenyl-phosphino)phenol HO(C 6H 4)PPh 2 in the presence of imidazole to give the corresponding complexes [Cp 2ZrCl(OC 6H 4PPh 2)], 1 and [Cp 2M(OC 6H 4PPh 2) 2] ( 2: MTi; 3: MZr). Under the same experimental conditions, the bulkier ligand 2-(diphenylphosphinomethyl)-4-methylphenol HO(C 6H 3-(CH 3)CH 2PPh 2 failed to react with [Cp 2MCl 2] (Ti or Zr) but with Cp 2Zr(CH 3) 2 gives the methyl complex [Cp 2Zr(CH 3){O(C 6H 3)(CH 3)CH 2PPh 2}], 4 and [Cp 2Zr[O(C 6H 3)(CH 3)CH 2PPh 2] 2], 5. Compounds 1 and 3 crystallize from CH 2Cl 2 solution, and their structures have been determined. The relatively short ZrO bond distance of 1.979(7) Å, and the ZrOC bond angle of 160.2(5)°, in one phenoxy ligand of 3 suggest significant double bonding between Zr and O atoms. Chemical reduction of 1 with Na/Hg gives the expected cyclic P-metallated Zr III species ▪ characterized by EPR ( g = 1.976; a( 31 P) = 14.6 G ). Preliminary data indicate that 3 acts as a diphosphine ligand upon reaction with [{Rh(CO) 2Cl} 2].

Studies on methylaluminoxane and ethylene polymerization

The preparation and structure of methylaluminoxane (MAO) was studied. MgCl 2·6H 2O was chosen as the new hydrolyzing agent for trimethylaluminium (TMA). The effects of the temperature, reaction time and ratio of MgCl 2·6H 2O to TMA on TMA hydrolyzing were observed. The yields of MAO were 23–50%. The molecular weights, determined cryoscopically in benzene, varied from 300 to 1700 and the degree of oligomerization from 6 to 30. MAO characterization was made using 1H-NMR, 13C-NMR spectroscopy. The Cp 2ZrCl 2/MAO catalyst system was used for ethylene polymerization. MAO prepared under different conditions had great influence on the activity of ethylene polymerization. The catalytic activity depended on the oligomerization degree of MAO. The catalytic activity and molecular weight ( M w) of polyethylene increased with increasing Al/Zr. The optimum polymerization temperature range for maximum activity was 60–70°C. The M w of polyethylene decreased with increasing polymerization temperature.

Zirconium catalyzed CC bond formation reaction of conjugated diynes with EtMgBr

The carbon-carbon bond formation reactions of diynes with EtMgBr can be catalysed by Cp 2ZrCl 2. The final products, magnesiated enynes, readily undergo stereoisomerization to give a mixture of (E) and (Z) isomers. The stoichiometric reaction of diynes with ethylene zirconocene gives zirconacyclopentenes with alkynyl substituents in the α position with high regioselectivities.

Novel head-to-tail alkyl-alkene or alkene-alkene coupling via zirconium-catalyzed reaction of alkylmagnesium derivatives with monosubstituted alkenes

The reaction of monosubstituted alkenes with alkylmagnesium derivatives catalyzed by Cp 2ZrCl 2 or related zirconocene derivatives provides head-to-tail alkyl-alkene or alkene-alkene coupling products, ∼50% of which are 2,5-dialkyl-4-pentenylmagnesium halides.

Polymerization of propene with catalyst systems composed of Al 2O 3 or MgCl 2-supported zirconocene and Al(CH 3) 3

Six kinds of heterogeneous catalysts were prepared by supporting iPr(Flu)(Cp)ZrCl 2 (1) and Cp 2ZrCl 2 (2) on Al 2O 3, MgCl 2 and SiO 2, and propene polymerization was conducted with these supported catalysts using a common alkylaluminium, Al(CH 3) 3, as cocatalyst. The 1 Al 2 O 3 and 1 MgCl 2 catalysts gave highly syndiotactic polypropylene whereas the 2 Al 2 O 3 and 2 MgCl 2 catalysts gave atactic polypropylene in fairly good yields. In contrast, the SiO 2-supported catalysts were found to be inactive for propene polymerization.

Reactions of fluorinated acid anhydrides with metal alkoxides and organometallic oxides

Reactions of (CF 3CO) 2O, (CF 3SO 2) 2O and (FSO) 2O with Zr(OCH 3) 4 at elevated temperatures resulted in the isolation of mixed ligand derivatives Zr(OCH 3) 2(O 2CCF 3) 2, Zr(OCH 3) 2(O 3SCF 3) 2 and Zr(OCH 3) 2(O 3SF) 2, respectively. However, reactions of these fluorinated acid anhydrides with Zr(OC 2H 5) 4 yielded previously known tetrakis derivatives Zr(O 2CCF 3) 4, Zr(O 3SCF 3) 4 and Zr(O 3SF) 4in quantitative yields. These fluorinated acid anhydrides react with φ 3SbO at ambient temperature to produce φ 3SbX 2 derivatives (X = CF 3COO,SO 3CF 3 or SO 3F) in quantitative yields. This is a fairly convenient route to prepare organometallic fluorosulfates which substantiates the potentiality of S 2O 5F 2 as a fluorosulfonating agent. The utility of such reactions and some reactions of (CF 3CO) 2O, (SO 2CF 3) 2O and (SO 2F) 2O with [Cp 2TiCl] 2O and [CP 2ZrCl] 2O leading to the isolation of novel or previously known compounds will be discussed.