Synthesis, mechanism and ethylene polymerization catalysis of Ge(iv), Sn(ii) and Zr(iv) complexes derived from substituted β-diketiminates

RSC Advances ◽  
2016 ◽  
Vol 6 (65) ◽  
pp. 60723-60728 ◽  
Author(s):  
Xia Xiao ◽  
Xiaomin Hao ◽  
Jianliang Bai ◽  
Jianbin Chao ◽  
Wei Cao ◽  
...  
Keyword(s):  
Ethylene Polymerization ◽  
Elimination Reaction ◽  
Synthesis Mechanism ◽  
X Ray ◽  
Polymerization Catalysis

Unusual X-ray characterized crystalline Sn(ii), Ge(iv) and Zr(iv) complexes have been prepared via a salt metathesis and elimination reaction.

Altering molecular weight distributions: Benzyl–phosphinimide titanium complexes as ethylene polymerization catalysts

2004 ◽  
Vol 82 (8) ◽  
pp. 1304-1313 ◽  
Author(s):  
Emily Hollink ◽  
Pingrong Wei ◽  
Douglas W Stephan
Keyword(s):  
Molecular Weight ◽  
Ethylene Polymerization ◽  
Active Species ◽  
Polymerization Catalysts ◽  
Subsequent Reaction ◽  
X Ray ◽  
Molecular Weight Distributions ◽  
Polymerization Catalysis ◽  
Weight Distributions ◽  
High Yields

The phosphines and corresponding phosphinimines R2BnPNSiMe3 (R = t-Bu, Cy), p-C6H4(CH2PR2)2 (R = t-Bu (1), Cy (2)), and p-C6H4(CH2PR2NSiMe3)2 (R = t-Bu (3), Cy (4)) were prepared in high yields. Subsequent reaction with Ti precursors afforded (R2BnPN)TiCp*Cl2 (Cp* = η-C5Me5; R = t-Bu (5), Cy (6)), (R2BnPN)TiCpCl2 (Cp = η-C5H5; R = t-Bu (7), Cy (8)), p-C6H4(CH2PR2NTiCp*Cl2)2 (R = t-Bu (9), Cy (10)), and p-C6H4(CH2PR2NTiCpCl2)2 (R = t-Bu (11), Cy (12)). Methylation of the above complexes gave (R2BnPN)TiCp*Me2 (R = t-Bu (13), Cy (14)), (R2BnPN)TiCpMe2 (R = t-Bu (15), Cy (16)), p-C6H4(CH2PR2NTiCp*Me2)2 (R = t-Bu (17), Cy (18)), and p-C6H4(CH2PR2NTiCpMe2)2 (R = t-Bu (19), Cy (20)). The activity of these species as catalyst precursors in ethylene polymerization catalysis was evaluated using Schlenk line and Buchi reactor techniques using activation by methylaluminoxane (MAO) or [Ph3C][B(C6F5)4]. All these catalysts showed good activities and yield polymers with relatively broad molecular weight distributions. The bimodal polymers derived from catalysts generated using MAO are proposed to result from additional active species, possibly as a result of reaction of MAO with the benzylic fragments. X-ray data are reported for 1, 4–8, 10, 12–14, 16, and 18–20.Key words: phosphinimides, polymerization, catalysis, polyethylene, titanium, polymer molecular weight distributions.

Synthese der Amide M[N(SiMetBu2)(SitBu3)] (M = Li, Na) durch N2-Eliminierung aus den Triazeniden M[tBu3SiNNNSiMetBu2] (M = Li, Na) / Synthesis of the Amides M[N(SiMetBu2)(SitBu3)] (M = Li, Na) by N2-Elimination Reaction of the Triazenides M[tBu3SiNNNSiMetBu2] (M= Li, Na)

2007 ◽  
Vol 62 (10) ◽  
pp. 1285-1290 ◽  
Author(s):  
Hans-Wolfram Lerner ◽  
Inge Sänger ◽  
Kurt Polborn ◽  
Michael Bolte ◽  
Matthias Wagner
Keyword(s):  
Solid State ◽  
Ambient Temperature ◽  
Benzene Solution ◽  
Elimination Reaction ◽  
X Ray

The thermolabile triazenides M[tBu3SiNNNSiMetBu2] (M = Li, Na) are accessible from the reaction of tBu2MeSiN3 with the silanides MSitBu3 (M = Li, Na) at −78 °C in THF. At r. t. N2 elimination from the triazenides M[tBu3SiNNNSiMetBu2] (M = Li, Na) takes place with the formation of M[N(SiMetBu2)(SitBu3)] (M = Li, Na). X-Ray quality crystals of Li(THF)[N(SiMetBu2)(SitBu3)] (orthorhombic, Pna21) are obtained from a benzene solution at ambient temperature. In contrast to the structures of the unsolvated silanides MSitBu3 (M = Li, Na), the THF adduct Li(THF)3SitBu3 is monomeric in the solid state (orthorhombic, Pna21).

Controlled Synthesis, Mechanism and Degradation Property of Birnessite-MnO2 Nanoflowers and Nanoflakes

2021 ◽  
Vol 21 (9) ◽  
pp. 4846-4851
Author(s):  
Xin-Li Hao ◽  
Yue-Hong Song ◽  
Lin-Yi Li ◽  
Lu-Feng Li ◽  
Shuo-Shuo Chang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Optical Property ◽  
Controlled Synthesis ◽  
Synthesis Mechanism ◽  
Oxidation Method ◽  
X Ray ◽  
Aqueous Oxidation ◽  
Degradation Properties ◽  
Scanning Electron

Birnessite-MnO2 nanoflakes were synthesized via an aqueous oxidation method at 90 °C using Mn(CH3COO)2, NaOH, and KMnO4. The samples’ morphology, crystalline structure, and optical property were determined by field emission scanning electron microscopy, X-ray powder diffraction and UV-Vis spectrophotometry. The birnessite-MnO2 nanoflakes were converted to KxMn8O16 and Mn suboxides following a decrease in the concentration of KMnO4 in the reaction. The amount of NaOH in the reaction determined the type of precursor. Without NaOH, the precursor was converted from Mn(OH)2 to Mn2+ (from Mn(CH3COO)2), thereby enabling the synthesis of birnessite-MnO2 nanoflowers. The formation mechanism of birnessite-MnO2 nanoflowers and nanoflakes was clarified via the corresponding simulated crystal structures. Evaluation of the synthesized samples confirmed that the birnessite-MnO2 nanoflakes and nanoflowers exhibited excellent degradation properties.

scholarly journals Molecular weight control in organochromium olefin polymerization catalysis by hemilabile ligand–metal interactions

2016 ◽  
Vol 12 ◽  
pp. 1372-1379 ◽  
Author(s):  
Stefan Mark ◽  
Hubert Wadepohl ◽  
Markus Enders
Keyword(s):  
Ethylene Polymerization ◽  
Weight Control ◽  
Transfer Reactions ◽  
High Catalytic Activity ◽  
Co Catalyst ◽  
Metal Centers ◽  
Molecular Weights ◽  
Metal Interactions ◽  
Polymerization Catalysis ◽  
Very High

A series of Cr(III) complexes based on quinoline-cyclopentadienyl ligands with additional hemilabile side arms were prepared and used as single-site catalyst precursors for ethylene polymerization. The additional donor functions interact with the metal centers only after activation with the co-catalyst. Evidence for this comes from DFT-calculations and from the differing behavior of the complexes in ethylene polymerization. All complexes investigated show very high catalytic activity and the additional side arm minimizes chain-transfer reactions, leading to increase of molecular weights of the resulting polymers.

scholarly journals Thermal Effect of Ceramic Nanofiller Aluminium Nitride on Polyethylene Properties

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
Omer Bin Sohail ◽  
P. A. Sreekumar ◽  
S. K. De ◽  
Masihullah Jabarullah Khan ◽  
Abbas Hakeem ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Ethylene Polymerization ◽  
Filler Loading ◽  
Aluminium Nitride ◽  
Thermal Gravimetric ◽  
X Ray Diffraction ◽  
Sem Images ◽  
Nano Composite ◽  
X Ray ◽  
Thermal Gravimetric Analyzer

Ethylene polymerization was done to form polyethylene nano-composite with nanoaluminum nitride using zirconocene catalysts. Results show that the catalytic activity is maximum at a filler loading of 15 mg nanoaluminum nitride. Differential scanning calorimeter (DSC) and X-ray diffraction (XRD) results show that percentage crystallinity was also marginally higher at this amount of filler. Thermal behavior of polyethylene nanocomposites (0, 15, 30, and 45) mg was studied by DSC and thermal gravimetric analyzer (TGA). Morphology of the component with 15 mg aluminium nitride is more fibrous as compared to 0 mg aluminium nitride and higher filler loading as shown by SEM images. In order to understand combustibility behavior, tests were performed on microcalorimeter. Its results showed decrease in combustibility in polyethylene nanocomposites as the filler loading increases.

Übergangsmetallkomplexe mit Schwefelliganden, LXXX. Synthese, Struktur, Oxotransfer- und redoxgekoppelte Kondensationsreaktionen von Molybdän-Oxo-Komplexen mit dem sterisch anspruchsvollen vierzähnigen Thioether-Thiolat-Liganden 'buS4'2- ('buS4'2- = 1,2-Bis(2-mercapto-3,5-di-t-butylphenylthio)ethan(2—))/Transition Metal Complexes with Sulfur Ligands, LXXX. Syntheses, Structures, Oxo Transfer and Redox Coupled Condensation Reactions of Molybdenum Oxo Complexes with the Sterically Demanding Tetradentate Thioether-Thiolato-Ligand 'buS4'2- ('buS4'2- = 1,2-Bis(2-mercapto-3,5-di-/-butylphenylthio)ethane(2—))

1992 ◽  
Vol 47 (1) ◽  
pp. 61-73 ◽  
Author(s):  
Dieter Sellmann ◽  
Franz Grasser ◽  
Falk Knoch ◽  
Matthias Moll
Keyword(s):  
Transition Metal ◽  
Transition Metal Complexes ◽  
Transfer Reaction ◽  
Parent Compound ◽  
Elimination Reaction ◽  
X Ray ◽  
Oxo Complexes ◽  
Sterically Demanding ◽  
Oxo Transfer ◽  
System 1

In order to obtain soluble molybdenum sulfur oxo complexes, [Mo(O)2('buS4')] (1) ('buS4'2- = 1,2-bis(2-mercapto-3,5-di-t-butylphenylthio)ethane(2-)) was synthesized by reaction of [Mo(O)2(acac)2] (acac- = acetylacetonate(1-) ) with 'buS4'-Li2. Treatment of 1 with PPh3 yielded [μ-O{Mo(O)('buS4')}2] (2) and OPPh3 in an oxo transfer reaction. [Mo(PMe3)2('buS2')2] (3) ('buS2'2- = 3,5-di-t-butyl-1,2 -benzenedithiolate(2-)) was obtained by twofold desoxygenation of 1 with excess PMe3 via a redox coupled addition elimination reaction. 2 reacts with the oxo group donor DMSO to yield 1 and Me2S. The system 1/2 then catalyses the oxo transfer reaction from DMSO to PPh3 and, therefore, shows properties modelling the co-factor in oxotransferases. In contrast to the parent compound [Mo(O)2('S4')] ('S4'2- = 1,2-bis(2-mercaptophenylthio)ethane(2-)), 1 is reactive towards hydrazine and its derivatives. Reactions with hydrazine and alkylhydrazines yield mixtures of products not containing nitrogen. By treatment of 1 with phenylhydrazine, the phenyldiazenido(1-) complex [Mo(NNPh)2('buS4')] (4) was formed in a redox coupled condensation. According to the X-ray structure analyses of 1, 2 and 4, the molybdenum centres in these complexes are coordinated pseudo-octahedrally by the four S-donors of the 'buS4'2- ligands, the oxo- and the N -donors.

scholarly journals Supersize Cp! Tetrabenzo[a,c,g,i]fluorenyl complexes of yttrium

2017 ◽  
Vol 95 (4) ◽  
pp. 363-370 ◽  
Author(s):  
Jianlong Sun ◽  
David J. Berg ◽  
Brendan Twamley
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Ethylene Polymerization ◽  
Nmr Studies ◽  
X Ray ◽  
X Ray Crystallography ◽  
Trinuclear Cluster ◽  
Polymerization Catalyst ◽  
Dynamic Nuclear Magnetic Resonance ◽  
Trimethylsilyl Isocyanate

The synthesis of tetrabenzo[a,c,g,i]fluorenyl (Tbf) yttrium dialkyl complexes, (Tbf)Y(CH2SiMe3)2(L) (L = tetrahydrofuran (THF), 1; L = bipy, 2), by direct protonolysis of the tris(alkyl) complex, Y(CH2SiMe3)3(THF)2, are reported. The X-ray crystal structures of 1 and 2 display the helical twisting typically observed for the Tbf ligand. Dynamic nuclear magnetic resonance (NMR) studies on 1 show a barrier to Tbf helical inversion (epimerization or “wagging”) of 38.1 ± 0.5 kJ mol−1. The reaction of 1 with acidic hydrocarbons such as 1,3-bis(trimethylsilyl)cyclopentadiene or trimethylsilylacetylene results in protonolysis to form the mixed Cp derivative [(Tbf){C5H3(SiMe3)2}Y(CH2SiMe3)(THF)] (3) or [(Tbf)Y(CCSiMe3)2(THF)]n (4), respectively. In the case of 4, a small amount of the trinuclear cluster (Tbf)Y3(μ3-CCSiMe3)2(μ2-CCSiMe3)3(CCSiMe3)3(THF)2 (5) was isolated and characterized by X-ray crystallography. Dialkyl 1 undergoes smooth insertion of trimethylsilyl isocyanate to afford [(Tbf)Y{κ2-(N,O)-Me3SiN(Me3SiCH2)CO}2(THF)] (6) but it does not react with alkenes. Treating 1 with [Ph3C]+[B(C6F5)4]− in bromobenzene generates a moderately active ethylene polymerization catalyst (36 kg mol−1 h−1 bar−1).

Ethylene Polymerization Catalysis by Vanadium-Based Systems Bearing Sulfur-Bridged Calixarenes

2011 ◽  
Vol 30 (21) ◽  
pp. 5620-5624 ◽  
Author(s):  
Carl Redshaw ◽  
Lucy Clowes ◽  
David L. Hughes ◽  
Mark R. J. Elsegood ◽  
Takehiko Yamato
Keyword(s):  
Ethylene Polymerization ◽  
Polymerization Catalysis
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