- Rhodium-catalysed hydroformylation of 1-octene using aryl and ferrocenyl Schiff base-derived ligands
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Monometallic and heterobimetallic complexes of Rh(I) bearing chelating N,O-bidentate aryl- and ferrocenyl-derived ligands have been synthesised via Schiff base condensation reactions, and characterised fully using 1H NMR, 13C{1H} NMR and Fourier transform infrared spectroscopies, elemental analysis and mass spectrometry. The new monometallic and heterobimetallic complexes were evaluated as potential catalyst precursors in the hydroformylation of 1-octene at 95°C and 40?bar. The ferrocenylimine mononuclear compounds were inactive in the hydroformylation experiments. The Rh(I) monometallic and the ferrocene–Rh(I) heterobimetallic pre-catalysts displayed good activity and conversion of 1-octene as well as outstanding chemoselectivity towards aldehydes in the hydroformylation reaction.
- Siangwata, Shepherd,Chulu, Sisasenkosi,Oliver, Clive L.,Smith, Gregory S.
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- Catalytic asymmetric epoxidation of unfunctionalised olefins using silica, LDH and resin-supported sulfonato-Mn(salen) complex
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Sulfonated chiral Mn(salen) catalyst immobilised onto various supports such as silica, LDH and resin afforded remarkably higher rates and ees of up to 96% for the asymmetric epoxidation of unfunctionalised olefins. The LDH and resin supported (R,R)-1 cata
- Choudary,Ramani, Thekkathu,Maheswaran,Prashant, Leon,Ranganath,Kumar, K. Vijay
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- The influence of comonomer on ethylene/α-olefin copolymers prepared using [bis(n-(3-tert butylsalicylidene)anilinato)] titanium (IV) dichloride complex
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We describe the synthesis of [bis(N-(3-tert-butylsalicylidene)anilinato)] titanium (IV) dichloride (Ti-FI complex) and examine the effects of comonomer (feed concentration and type) on its catalytic performance and properties of the resulting polymers. Ethylene/1- hexene and ethylene/1-octene copolymers were prepared through copolymerization using Ti-FI catalyst, activated by MAO cocatalyst at 323 K and 50 psi ethylene pressure at various initial comonomer concentrations. The obtained copolymers were characterized by DSC, GPC and 13C-NMR. The results indicate that Ti-FI complex performs as a high potential catalyst, as evidenced by high activity and high molecular weight and uniform molecular weight distribution of its products. Nevertheless, the bulky structure of FI catalyst seems to hinder the insertion of a-olefin comonomer, contributing to the pretty low comonomer incorporation into the polymer chain. The catalytic activity was enhanced with the comonomer feed concentration, but the molecular weight and melting temperature decreased. By comparison both sets of catalytic systems, namely ethylene/1-hexene and ethylene/1-octene copolymerization, the first one afforded better activity by reason of easier insertion of short chain comonomer. Although 1-hexene copolymers also exhibited higher molecular weight than 1-octene, no significant difference in both melting temperature and crystallinity can be noticed between these comonomers.
- Kaivalchatchawal, Patcharaporn,Kaivalchatchawal, Pattiya,Samingprai, Sutheerawat,Praserthdam, Piyasan,Jongsomjit, Bunjerd
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- Di- and trinuclear iron/titanium and iron/zirconium complexes with heterocyclic ligands as catalysts for ethylene polymerization
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The properties of polyolefin resins depend very much on their molecular weights, the amount of side chain branchings and molecular weight distributions. One way to obtain such tailored products in only one reaction step consists in the application of dissymmetric multi nuclear catalysts with different active sites. Since every active site is producing its own polymer, a “molecular blending” is the result. In order to reach this goal, a variety of mono, di- and trinuclear complexes of iron, titanium and zirconium, containing 2,6-bis(aryliminoethyl)pyridine and phenoxyimine building blocks have been synthesized and characterized. The reaction of iodo functionalized 2,6-bis(arylimino-ethyl)pyridine derivatives with alkyne functionalized phenoxyimine compounds via Sonogashira cross-coupling reactions results in ligand precursors that can provide coordination sites for two different metals. Trinuclear complexes with the combinations Ti/Fe and Zr/Fe, each molecule containing two iron atoms in two 2,6-bis(aryliminoethyl)pyridine units, gave the best ethylene polymerization results. Due to fast ligand exchange reactions, dinuclear iron/titanium complexes could not be isolated from reactions of mono(phenoxyimine) titanium complexes and the coupled bis(chelate) ligand precursor. Since the metal centers show their best performances at different polymerization temperatures, the compositions (and, therefore, the molecular weight distributions) of the desired polyethylenes may be adjusted by a simple change of the reaction temperature.
- G?rl, Christian,Betthausen, Eva,Alt, Helmut G.
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- Aqueous-phase hydroformylation of 1-octene using hydrophilic sulfonate salicylaldimine dendrimers
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Water-soluble dendritic ligands based on tris-2-(5-sulfonato salicylaldimine ethyl)amine (5) and DAB-(5-sulfonato salicylaldimine) (6) (DAB = diaminobutane) were synthesized by means of Schiff base condensation and sulfonation reactions. These dendritic l
- Hager, Emma B.,Makhubela, Banothile C.E.,Smith, Gregory S.
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p. 13927 - 13935
(2013/01/15)
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- A new heterogeneous chiral (salen)manganese(III) system for enantioselective epoxidation of non-functionalized olefins
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This communication describes the design and application of a novel catalytic epoxidation system derived from the initial immobilization of a homogeneous sulfonato (salen)Mn(III) complex on two solid carriers (silica gel and siliceous earth) and subsequent dispersion of the supported manganese complexes into ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMImPF6) and 1-butyl-3-methylimidazolium tetrafluoroborate (BMImBF4) for recycling. The performance of chiral (salen)Mn(III) system in enantioselective epoxidation of olefins was investigated systematically. Even higher enantioselectivity than that of the homogeneous counterpart was obtained with similar catalytic activity. In particular, the best catalytic result is that the combination of the silica gel-supported (salen)Mn(III) catalyst and BMImPF6 affords 97-100% ee for epoxidation of α-methylstyrene, and high ee values were retained even after three cycles.
- Wei, Saili,Tang, Yuhai,Xu, Xiaoqian,Xu, Guojin,Yu, Yong,Sun, Yang,Zheng, Yuansuo
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experimental part
p. 146 - 153
(2012/06/29)
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- Awakening a dormant catalyst: Salicylaldimine systems for ethene/tert-butylstyrene copolymerization
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A group of readily available zirconium catalysts incapable of ethene-co-styrene polymerization are remarkably active and selective for the production of the new polymer ethene-co-tert-butylstyrene via a single site mechanism.
- Theaker, Giles W.,Morton, Colin,Scott, Peter
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supporting information; experimental part
p. 6883 - 6885
(2009/04/13)
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- A family of zirconium complexes having two phenoxy - imine chelate ligands for olefin polymerization
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A zirconium complex having two phenoxy - imine chelate ligands, bis[N-(3-tert-butylsalicylidene)-anilinato]zirconium(IV)dichloride (1), was found to display a very high ethylene polymerization activity of 550 kg of polymer/mmol of cat·h with a viscosity average molecular weight, (Mv) value of 0.9 × 104 at 25 °C at atmospheric pressure using methylalumoxane (MAO) as a cocatalyst. This activity is 1 order of magnitude larger than that exhibited by Cp2ZrCl2 under the same polymerization conditions. The use of Ph3CB(C6F5)4/i-Bu3Al in place of MAO as a cocatalyst resulted in extremely high molecular weight polyethylene, Mv 505 × 104, with an activity of 11 kg of polymer/mmol of cat·h at 50 °C. This Mv value is one of the highest values displayed by homogeneous olefin polymerization catalysts. Complex 1, using Ph3CB(C6F5)4/i-BU3Al as a cocatalyst, provided a high molecular weight ethylene-propylene copolymer, Mv 109 × 104, with 8 kg of polymer/mmol of cat·h activity at a propylene content of 20.7 mol %. X-ray analysis revealed that complex 1 adopts a distorted octahedral coordination structure around the zirconium metal and that two oxygen atoms are situated in trans position while two nitrogen atoms and two chlorine atoms are situated in cis position. DFT calculations suggest that the active species derived from complex 1 possesses two available cis-located sites for efficient ethylene polymerization. Changing the tert-butyl group in the phenoxy benzene ring enhanced the polymerization activity. Bis[N-(3-cumyl-5-methylsalicylidene)cyclohexylaminato]zirconium(IV)dichloride (7) with MAO displayed an ethylene polymerization activity of 4315 kg of polymer/mmol of cat·h at 25 °C at atmospheric pressure. This activity corresponds to a catalyst turnover frequency (TOF) value of 42 900/s· atm. This TOF value is one of the largest not only for olefin polymerization but also for any known catalytic reaction. Ligands with additional steric congestion near the polymerization reaction center gave increased Mv values. The maximum Mv value, 220 × 104 using MAO, was obtained with bis[N-(3,5-dicumylsalicylidene)-2′-isopropylanilinato]zirconium (IV)dichloride (15). Thus, polyethylenes ranging from low to exceptionally high molecular weights can be obtained from these zirconium complexes by changing the ligand structure and the choice of cocatalyst.
- Matsui,Mitani,Saito,Tohi,Makio,Matsukawa,Takagi,Tsuru,Nitabaru,Nakano,Tanaka,Kashiwa,Fujita
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p. 6847 - 6856
(2007/10/03)
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