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The reaction of indenyllithium, IndLi, with CpMCl3 (M = Ti, Zr) or Cp*MCl3 (M = Zr, Hf) leads to complexes of the type (L)(Ind)MCl2 (1: L = Cp, M = Ti; 2: L = Cp, M = Zr; 3: L = Cp*, M = Zr; 4: L = Cp*, M = Hf). In combination with methylaluminoxan (MAO), complexes 1-4 show a high catalytic activity as homogeneous ethylene polymerization catalysts. The ethylene selective catalyst precursor 3 was characterized by an X-ray structure analysis.
- Schmid, Michael A.,Alt, Helmut G.,Milius, Wolfgang
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- Neutral dimethylzirconocene complexes as initiators for the ring-opening polymerization of ε-caprolactone
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The synthesis, structures, and ring-opening polymerization (ROP) activity of new dimethyl-ansa- and -non-ansa-zirconocene complexes are reported. The substituted indene precursors 1-C9H7R [R = CH3 (1), CH2Ph (2) and C2H4(C4H 7O2) (3)] were synthesised by treating RBr [R = CH 2Ph and C2H4(C4H7O 2)] or MeI with indenyllithium. Likewise, bridged indenyl/cyclopentadiene compounds [Me2Si(3-C9H 6R)(C5Me4H)] [R = H (4), CH3 (5), CH2Ph (6) and C2H4(C4H 7O2) (7)] were obtained by treating the lithium salt of the appropriately substituted indene with ClSiMe2(C 5Me4H). ansa-Indenyl-cyclopentadienylmetallocenes [Zr{Me2Si(3-η5-C9H5R) (η5-C5Me4)}Cl2] [R = H (8), CH3 (9), CH2Ph (10), C2H4(C 4H7O2) (11)] were subsequently obtained by treating the dilithium salts of the corresponding ligands with ZrCl4 in toluene. The dimethyl derivatives [Zr{Me2Si(3-η5- C9H5R)(η5-C5Me 4)}Me2] [R = H (12), CH3 (13), CH2Ph (14), C2H4(C4H7O2) (15)] were prepared by treating the corresponding ansa-zirconocene dichloride complex with MgMeBr. Dialkyl derivative [Zr{Me2Si{3-η5-C 9H5(CH2Ph)}(η5-C 5Me4)}(CH2SiMe3)2] (16) was prepared by adding 2 equiv. of LiCH2SiMe3 to complex 10. Mixed indenyl/cyclopentadienylzirconocene complexes [Zr(η5- C9H6R)(η5-C5H 5)Cl2] [R = H (17), C2H4(C 4H7O2) (18)] were prepared by treating the lithium salt of the appropriately substituted indene with [Zr(η5- C5H5)Cl3]. Likewise, dimethyl derivatives [Zr(η5-C9H6R)(η5-C 5H5)Me2] [R = H (19), C2H 4(C4H7O2) (20)] were prepared by treating the corresponding mixed indenyl/cyclopentadienyl dichloride complex with 2 equiv. of MgMeBr. The X-ray crystal structures of 7, 12, and 13 were also established. Finally, comparative catalytic studies of zirconium complexes 12-16, 19 and 20 in ROP reactions of ε-caprolactone are described. Synthesis, characterization, and catalytic studies of new dimethyl-ansa- and -non-ansa-zirconocene complexes for ring-opening polymerization of ε-caprolactone are described. Copyright
- Villasenor, Elena,Gutierrez-Gonzalez, Ruben,Carrillo-Hermosilla, Fernando,Fernandez-Galan, Rafael,Lopez-Solera, Isabel,Fernandez-Pacheco, Ana Rodriguez,Antinolo, Antonio
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p. 1184 - 1196
(2013/04/10)
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- Synthesis of racemic chiral-at-metal complexes of the Group 4 metals
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A protocol for asymmetric synthesis of chiral-at-metal complexes is described, but enantiomerically-enriched products can not be isolated due to formation of complexes between the Group 4 metallocene products and the borane by-products. An efficient method for synthesis of racemic chiral-at-metal metallocenes, through lithium chloride catalysed ligand redistribution reactions, is described. Sterically-hindered racemic chiral-at-metal complexes are prepared by nucleophilic substitution of prochiral dichlorides.
- Alcock, Nathaniel W.,Clase, Howard J.,Duncalf, David J.,Hart, Suzanne L.,McCamley, Andrew,McCormack, Peter J.,Taylor, Paul C.
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- DITHIOCARBAMATE ANIONS AS SALTS OF OXINATE CHELATES OF ZIRCONIUM(IV)
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(η5-cycopentadienyl) (η5-pyrrolyl) zirconium(IV) dichloride, (η5-pyrrolyl)zirconium(IV)dichloride and (η5-cyclopentadienyl)(η5-indenyl)zirconium(IV) dichloride, when treated with 8-hydroxyquinoline (oxine) in aqueous medium form ionic derivatives of the type, 5-R)(η5-R')ZrL>(1+)Cl(1-) (R = C5H5, C9H7, R'= C4H4N; R = C5H5, R'= C9H7; L is a conjugate base of oxine.These react with dithiocarbamate anions in aqueous solution, giving ionic complexes of the type, 5-R)(η5-R')ZrL>(1+)X(1-) (X= Me2NCS2, Et2NCS2 and iPr2NCS2).IR and 1H-NMR studies demonstrate that ligand L is chelating in all the cases.Consequently there is tetrahedral coordination around the zirconium(IV) ion.
- Sodhi, G. S.,Kumar, S.,Kaushik, N. K.
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p. 329 - 336
(2007/10/02)
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