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Tshuva, Edit Y.; Goldberg, Israel; Kol, Moshe; Goldschmidt, Zeev

doi:10.1039/b105492a

Cited by 126 publications

(118 citation statements)

References 25 publications

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“…In previous articles we have described the synthesis of [ONNO]-type amine bis(phenolate) complexes of oxo-vanadium(v) [1][2][3] and vanadium(iv) [4][5]. [15,16] Although vanadium complexes with oxidation numbers from +3 to +5 are known to catalyze ethylene polymerization, the active speEthylene Homo-and Copolymerization Activity of a Series of Vanadium(ii-iv) Catalysts FULL PAPER cies is probably a vanadium(iii) complex.…”

Section: Resultsmentioning

confidence: 99%

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Ethylene Homo‐ and Copolymerization Activity of a Series of [ONNO]‐Type Amine Bis(phenolate) Based Vanadium(II–V) Catalysts

et al. 2005

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The synthesis and structural characterization of new paramagnetic amine bis(phenolate) [ONNO]-vanadium(III) and -vanadium (II) complexes, V III (acac) [ONNO], V III (Cl) (THF) [ONNO], and V II (TMEDA)[ONNO], is described. These compounds complete the family of [ONNO]-vanadium(IV/V) complexes previously reported. The members of the [ONNO]-vanadium family at various oxidation states that range from vanadium(II) to vanadium(V), in association with IntroductionIn the past decade, a tremendous amount of effort has been devoted to the design of new "non-metallocene" group 4 transition metal complexes because of their importance as α-olefin polymerization catalysts.[1] Particularly, chelating diamide, [1a,2-4] dialkoxide, [1a,5-6] or phenoxyimine [7,8] ligands have been extensively studied as rigid supporting environments for titanium and zirconium complexes, which has resulted in the emergence of a great deal of novel and useful chemistry, including the discovery of highly active olefin polymerization precatalysts. Among these new ligands, chelating, dianionic [ONNO]-type amine bis(phenolate) ligands associated with group 4 metal complexes [5] have proven to be highly active 1-hexene polymerization catalysts, and in some cases, even isospecific living polymerization was possible.[5a] Recently yttrium-[ONNO] complexes have been reported for their catalytic activity in the ring-opening polymerization of ε-caprolactone. [9] Vanadium-based catalysts in homogeneous ZieglerNatta polymerization have been known for about half a century.[10] Although generally less active, their use presents a number of interesting advantages over group 4 metal catalysts: [11] (i) the synthesis of high molecular weight polymers with narrow polydispersity, (ii) the preparation of ethylene/ α-olefin copolymers with high α-olefin incorporation, and (iii) the preparation of syndiotactic polypropylene. The major reason for the low activity of these systems is their deactivation during the polymerization process, probably due to reduction of the catalytically active vanadium species [a] 2850EtAlCl 2 cocatalyst, were studied in the polymerization of ethylene and in the copolymerizations of ethylene-1-hexene and ethylene-norbornene. Poly(ethylene-co-1-hexene) and poly(-ethylene-co-norbornene) were produced with co-monomer content of up to 11 mol-% and 29 mol-% for 1-hexene and norbornene, respectively. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) to low-valent, less active or inactive species. Nevertheless, V(acac) 3 is currently employed in the synthesis of EP (ethylene-propylene) and EPDM (ethylene-propylene-diene monomer) elastomers.As part of an ongoing study of vanadium chemistry with various supporting ligands, [12] and in particular of vanadium complexes for olefin polymerization, we have recently used ancillary diamido ligands with sterically demanding protecting groups [13] or imido ligands [14] on vanadium(iv) complexes as a way to overcome the problem of catalyst deactivation by stabilization of the formal ...

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Section: Resultsmentioning

confidence: 99%

“…Among these new ligands, chelating, dianionic [ONNO]-type amine bis(phenolate) ligands associated with group 4 metal complexes [5] have proven to be highly active 1-hexene polymerization catalysts, and in some cases, even isospecific living polymerization was possible.…”

Section: Introductionmentioning

confidence: 99%

Ethylene Homo‐ and Copolymerization Activity of a Series of [ONNO]‐Type Amine Bis(phenolate) Based Vanadium(II–V) Catalysts

et al. 2005

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“…Starting materials for the synthesis of ligand precursors 1-7 were purchased from Aldrich and were used without further purification. 2-Adamantyl-4-tert-butylphenol [27] and ligands 2 and 3 [28] were prepared by reported methods. Ligands 1 and 4-7 were synthesized by modifications of the methods reported in the literature.…”

Section: Methodsmentioning

confidence: 99%

Ring‐Opening Polymerization of Lactide with Group 3 Metal Complexes Supported by Dianionic Alkoxy‐Amino‐Bisphenolate Ligands: Combining High Activity, Productivity, and Selectivity

Amgoune

Thomas

Roisnel

et al. 2005

Chemistry A European J

399

215

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A series of new alkoxy-amino-bis(phenols) (H2L 1-6) has been synthesized by Mannich condensations of substituted phenols, formaldehyde, and amino ethers or diamines. The coordination properties of these dianionic ligands towards yttrium, lanthanum, and neodymium have been studied. The resulting Group 3 metal complexes have been used as initiators for the ring-opening polymerization of rac-lactide to provide poly(lactic acid)s (PLAs). The polymerizations are living, as evidenced by the narrow polydispersities of the isolated polymers, together with the linear natures of number average molecular weight versus conversion plots and monomer-to-catalyst ratios. Complex [Y(L6){N(SiHMe2)2}(THF)] (17) polymerized rac-lactide to heterotactic PLA (Pr = 0.90 at 20 degrees C) and meso-lactide to syndiotactic PLA (Pr = 0.75 at 20 degrees C). The in situ formation of [Y(L6)(OiPr)(THF)] (18) from 17 and 2-propanol resulted in narrower molecular weight distributions (PDI = 1.06). With complex 18, highly heterotactic PLAs with narrow molecular weight distributions were obtained with high activities and productivities at room temperature. The natures of the ligand substituents were shown to have a significant influence on the degree of control of the polymerizations, and in particular on the tacticity of the polymer.

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“…[81] as in 1-olefin polymerization by Ti IV catalysis. [82][83][84][85][86] Various constitutions of branched and sequential modes can be employed by varying the connectivity of the N atoms (Scheme 8). In addition, various different coordination numbers (such as 7 or 8) may be explored by incorporating additional dative N atoms, and different ratios of covalent/ coordinative donors may also affect the number of labile ligands in the end complex.…”

Section: Ligand and Complex Designmentioning

confidence: 99%

Cytotoxic Titanium(IV) Complexes: Renaissance

Tshuva

Ashenhurst

2009

Eur J Inorg Chem

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In this paper we overview our studies on amine–phenolato TiIV complexes as cytotoxic agents, in the context of the results reported thus far with titanocene dichloride, budotitane and derivatives. In particular, we emphasize the studies about the structure–activity relationship performed and important insights gained with the known compounds and our complexes, in regards to their hydrolytic behavior and cytotoxic activity, while pointing to potential mechanistic aspects. Titanocene dichloride and budotitane show cytotoxic activity towards cells that are resistant to cisplatin with reduced side effects. Their main drawback is their hydrolytic instability that has impeded mechanistic investigations and pharmaceutical use. Our new family of cytotoxic complexes was designed to include a single highly electron‐donating chelating ligand to afford octahedral TiIV complexes of relatively high hydrolytic stability, with the aim to retain ligand binding throughout the biological activity for achieving controlled processes and allowing mechanistic evaluation. The effect of several parameters on hydrolysis and cytotoxicity were investigated, including those relating to the tetradentate ligand and those relating to the labile groups. Overall we observed high cytotoxic activity that is strongly dependent on the ligand, and which is strongly correlated to the complex hydrolytic behavior. Additional mechanistic studies provide insights regarding the time frame of activity and cell penetration. Some comparisons to titanocene dichloride, budotitane and analogues are highlighted.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

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Cited by 126 publications

References 25 publications

Ethylene Homo‐ and Copolymerization Activity of a Series of [ONNO]‐Type Amine Bis(phenolate) Based Vanadium(II–V) Catalysts

Ethylene Homo‐ and Copolymerization Activity of a Series of [ONNO]‐Type Amine Bis(phenolate) Based Vanadium(II–V) Catalysts

Ring‐Opening Polymerization of Lactide with Group 3 Metal Complexes Supported by Dianionic Alkoxy‐Amino‐Bisphenolate Ligands: Combining High Activity, Productivity, and Selectivity

Cytotoxic Titanium(IV) Complexes: Renaissance

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