The combination of mononuclear metallocene and phenoxyimine complexes to give trinuclear catalysts for the polymerization of ethylene

Görl, Christian; Alt, Helmut G.

doi:10.1016/j.jorganchem.2007.10.001

Cited by 29 publications

(26 citation statements)

References 43 publications

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“…[1] In the field of multinuclear catalysts for polymerization of olefins, many studies have been reported. [6][7][8][9] Higher or lower activity and selectivity of multinuclear catalysts in comparison to mononuclear ones can be attributed to the presence of adjacent metal centers or the ligand structure, all of which effects could be interpreted as steric and electronic effects. [2][3][4][5] However, in other cases, a broad to bimodal molecular weight distribution has been reported.…”

Section: Introductionmentioning

confidence: 99%

Cooperative effect through different bridges in nickel catalysts for polymerization of ethylene

Khoshsefat

Dechal

Ahmadjo

et al. 2019

Applied Organom Chemis

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A series of mononuclear (M 1 and M 2 ) and dinuclear (C 1 -C 6 ) Ni α-diimine catalysts activated by modified methylaluminoxane were used in polymerization of ethylene. Catalyst C 2 bearing the optimum bulkiness showed the highest activity (1.6 × 10 6 g PE (mol Ni) −1 h −1 ) and the lowest short-chain branching (32.5/1000 C) in comparison to the dinuclear and mononuclear analogues.Although the mononuclear catalysts M 1 and M 2 polymerized ethylene to a branched amorphous polymer, the dinuclear catalysts led to different branched semicrystalline polyethylenes. Homogeneity and heterogeneity in the microstructure of the polyethylene samples was observed. Different trends for each catalyst were assigned to syn and anti stereoisomers. In addition, thermal behavior of the samples in the successive self-nucleation and annealing technique exhibited different orders and intensities from methylene sequences and lamellae thickness in respect of each stereoisomer behavior. Higher selectivity of hexyl branches obtained by catalyst C 2 showed a cooperative effect between the centers. The results also revealed that for catalysts C 5 and C 6 , selectivity of methyl branches led to very high endotherms and crystalline sequences with melting temperatures higher than that of 100% crystalline polyethylene indicating ethylene/propylene copolymer analogues. For catalysts C 3 and C 4 , more vinyl end groups were a result of the long distance between the Ni centers. Kinetic profiles of polymerization along with a computational study of the precatalysts and catalysts demonstrated that there is a direct relation between rate constant, energy interval of catalyst and precatalyst, and interaction energy of Et···methyl cationic active center (Et···MCC or π-Comp.). Based on this, narrow energy interval (activation energy) of precatalyst and catalyst leads to fast and higher activation rate (catalyst M 2 ), and strong interaction of ethylene and catalyst leads to high monomer uptake and productivity (catalyst C 2 ). Moreover, theoretical parameters including electron affinity, Mulliken charge on Ni, chemical potential and hardness, and global electrophilicity showed optimum values for C 2 .

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Section: Introductionmentioning

confidence: 99%

Cooperative effect through different bridges in nickel catalysts for polymerization of ethylene

Khoshsefat

Dechal

Ahmadjo

et al. 2019

Applied Organom Chemis

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“…Dibromoalkanes (7)(8)(9) were reacted with sodium azide to 10 prepare bis azides (10-12) in situ, which were subsequently coupled with 5-hexyn-2-one (13) 13 to afford the diketones (14)(15)(16) Figure 1 The X-ray crystal structure of the methanol solvate of compound 5. Non-acidic hydrogen atoms have been omitted for clarity.…”

mentioning

confidence: 99%

“…The introduction of one triazole hydrogen bond 30 donor group into the strap results in an improvement of the affinity by a factor of 10 (entries 1, 4) however the incorporation of a second yields only a rather marginal gain (entry 13). Surprisingly the second triazole moiety scarcely contributes to the overall enthalpy of binding (entries 4 versus 35 13,19,25). Lengthening the distance between the triazole modules diminishes the enthalpic interaction, whilst concomitantly raising the entropic component to more positive values by an equivalent amount.…”

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Calix[4]pyrrole-based anion transporters with tuneable transport properties

et al. 2010

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Three new bis-1,2,3-triazole strapped calix [4]pyrroles have been prepared via 'click' chemistry and their anion complexation and lipid bilayer transport properties studied by a combination of single crystal X-ray diffraction studies, 1 H NMR titration techniques, isothermal titration calorimetry and lipid bilayer anion transport studies in POPC vesicles. Bilayer transport efficiency for transmembrane chloride transport was found to directly depend on the length of the alkyl chain present in the bis-triazole strap.

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“…Benzofulvenes are valuable compounds that have found various applications in organometallic chemistry as precursors of indenyl ligands, [1] and in materials science. [2] Their preparations traditionally rely on the transformation of indane [1a] or indanone derivatives.…”

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confidence: 99%

Silver and Brønsted Acid Catalyzed Nazarov‐Type Cyclizations To Generate Benzofulvenes

et al. 2009

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The combination of mononuclear metallocene and phenoxyimine complexes to give trinuclear catalysts for the polymerization of ethylene

Cited by 29 publications

References 43 publications

Cooperative effect through different bridges in nickel catalysts for polymerization of ethylene

Cooperative effect through different bridges in nickel catalysts for polymerization of ethylene

Calix[4]pyrrole-based anion transporters with tuneable transport properties

Silver and Brønsted Acid Catalyzed Nazarov‐Type Cyclizations To Generate Benzofulvenes

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