The Stereochemistry of Organometallic Compounds. XXXI. Hydrocyanation of Alkynols

1988 ◽  
Vol 41 (7) ◽  
pp. 1099 ◽  
Author(s):  
WR Jackson ◽  
CG Lovel ◽  
P Perlmutter ◽  
AJ Smallridge
Keyword(s):  
Organometallic Compounds ◽  
Catalyst System ◽  
Steric Effects ◽  
Triphenyl Phosphite ◽  
Catalyst Systems

The regioselectivity of hydrocyanation of a range of alkynols using nickel-based catalyst systems involving either triphenyl phosphite or α,α′-bis(diphenylphosphino)-o-xylene (phmep) has been investigated. The regioselectivity of the hydrocyanations involving the phosphine catalyst reflected dominant steric effects whereas results from the phosphite catalyst system showed some evidence for chelation control. Yields of nitriles from reactions based on the phosphite system were variable, whereas moderate to good yields of distilled products could be obtained consistently by using the phosphine -based system. An explanation for this variation in yield is proposed.

Niobium(v) chloride and imidazolium bromides as efficient dual catalyst systems for the cycloaddition of carbon dioxide and propylene oxide

2014 ◽  
Vol 4 (6) ◽  
pp. 1638-1643 ◽  
Author(s):  
Michael E. Wilhelm ◽  
Michael H. Anthofer ◽  
Robert M. Reich ◽  
Valerio D'Elia ◽  
Jean-Marie Basset ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Catalytic Activity ◽  
Propylene Oxide ◽  
Catalyst System ◽  
Cyclic Carbonates ◽  
Imidazolium Salt ◽  
Catalyst Systems

Imidazolium bromides combined with niobium(v) choride were used as catalyst system for the reaction of CO2 with epoxides to cyclic carbonates. The variation of the cation structure strongly affects the properties of the imidazolium salt and therefore the catalytic activity.

Steric effects in organometallic compounds. A 103Rh NMR study of alkylrhodoximes

1996 ◽  
Vol 513 (1-2) ◽  
pp. 193-200 ◽  
Author(s):  
Fioretta Asaro ◽  
Giacomo Costa ◽  
Renata Dreos ◽  
Giorgio Pellizer ◽  
Wolfgang von Philipsborn
Keyword(s):  
Organometallic Compounds ◽  
Steric Effects ◽  
Nmr Study

Chromium-Based Catalyst for Ethylene Tetramerization to 1-Octene

2011 ◽  
Vol 347-353 ◽  
pp. 3392-3395
Author(s):  
Bao Jun Zhang ◽  
Bu Wei Yu ◽  
Gang Wang ◽  
Jian Zhong Li ◽  
Si Han Wang ◽  
...  
Keyword(s):  
Catalyst System ◽  
Ethylene Oligomerization ◽  
Steric Effects ◽  
Molar Ratio ◽  
Ethylene Tetramerization ◽  
Electric Effects

Novel diphoshinoamine(PNRNP) ligands have been used in ethylene oligomerization with Cr(III) compounds and cocatalyst. The results indicate that the catalyst system can yield 1-octene in selectivities up to 80%. Another novel diphoshinoamine ligands (((Ar2P)2N)2R)(R=cyclopropylamine) also were synthesized and characterized. Factors which affect the result of ethylene tetramerisation, such as cocatalyst, temperature, pressure and the molar ratio of Al/Cr were examined. Steric effects and electric effects were also considered in this report.

Study of rare-earth π-complexes by means of Voronoi–Dirichlet polyhedra

2001 ◽  
Vol 57 (3) ◽  
pp. 261-270 ◽  
Author(s):  
O. A. Blatova ◽  
V. A. Blatov ◽  
V. N. Serezhkin
Keyword(s):  
Rare Earth ◽  
Oxidation State ◽  
Topological Analysis ◽  
Organometallic Compounds ◽  
Domain Size ◽  
Steric Effects ◽  
Novel Method ◽  
Complexes Of Rare Earth

An investigation of 135 π-complexes of rare-earth atoms (Ln) was carried out with Voronoi–Dirichlet polyhedra. A novel method for the evaluation of the sizes of polyatomic ligands and steric effects in the structure of organometallic compounds was developed. The dependence of the domain size for Ln atoms on their nature, coordinating number and oxidation state was studied. The reasons for the occurrence of agostic Ln—H contacts were considered with a geometrical–topological analysis.

Dependence of Tack Strength on Molecular Properties

1959 ◽  
Vol 32 (1) ◽  
pp. 48-66 ◽  
Author(s):  
W. G. Forbes ◽  
L. A. McLeod
Keyword(s):  
Molecular Weight ◽  
Shear Viscosity ◽  
Catalyst System ◽  
Chain Entanglement ◽  
Molecular Weights ◽  
Styrene Copolymers ◽  
The Difference ◽  
Catalyst Systems ◽  
Time Required ◽  
Butadiene Styrene

Abstract A method has been developed for the measurement of the tack strength of fresh and reproducibly smooth rubber surfaces. Using this method the tack strength of natural rubber is shown to be independent of polymer purity, and, to a large extent, Mooney viscosity, intrinsic viscosity, gel content and molecular weight distribution. The relative tack strengths of polyisoprenes of different molecular weights prepared in different catalyst systems are measured. The results are discussed in terms of microstructure. A study of the tack strength of oil-extended butadiene-styrene copolymers indicates that relative tack strength is related to the shear viscosity of the bulk polymer. Measurements of relative tack strength on Alfin and free radical butadiene-styrene copolymers, butyl, brominated butyl and butadiene-acrylonitrile copolymers confirm the inportance of shear viscosity in controlling tack strength. Choice of catalyst system and temperature of polymerization cause the largest variation in polymer viscosity. The contact time required for the relative tack strength to become unity is shown to be inversely dependent upon the value of the relative tack strength itself. Shear viscosity measurements are given for six classes of polymer and the values shown to correlate with relative tack strength. It is postulated that molecular weight (and probably also chain entanglement) is the controlling variable. The bond strength between two different uncured polymers is shown to depend upon the difference in cohesive energy densities of the two polymers.

scholarly journals A Comparative Study of Carbon Nanotubes Synthesized from Co/Zn/Al and Fe/Ni/Al Catalyst

2011 ◽  
Vol 8 (3) ◽  
pp. 1014-1021 ◽  
Author(s):  
Ezekiel Dixon Dikio
Keyword(s):  
Carbon Nanotubes ◽  
Raman Spectroscopy ◽  
Electron Microscope ◽  
Thermogravimetric Analysis ◽  
Catalyst System ◽  
X Ray ◽  
Transmission Electron ◽  
Catalyst Systems ◽  
Synthesis Of Carbon Nanotubes ◽  
Scanning Electron

The catalyst systems Fe/Ni/Al and Co/Zn/Al were synthesized and used in the synthesis of carbon nanotubes. The carbon nanotubes produced were characterized by Field Emission Scanning Electron Microscope(FE-SEM), Energy Dispersive x-ray Spectroscopy(EDS), Raman spectroscopy, Thermogravimetric Analysis(TGA)and Transmission Electron Microscope(TEM). A comparison of the morphological profile of the carbon nanotubes produced from these catalysts indicates the catalyst system Fe/Ni/Al to have produced higher quality carbon nanotubes than the catalyst system Co/Zn/Al.

Copolymerization of 5-norbornene-2-metheneoxy-trimethylsilyl with methyl 5-norbornene-2-carboxylate catalyzed by a novel Ni(benzocyclohexan-ketonaphthylimino)2/B(C6F5)3) system

2012 ◽  
Vol 32 (6-7) ◽  
pp. 415-423
Author(s):  
Xiaofeng Wang ◽  
Xiaohui He ◽  
Defu Chen ◽  
Yiwang Chen
Keyword(s):  
Thermal Stability ◽  
Molecular Weight ◽  
Nmr Spectra ◽  
Catalyst System ◽  
Narrow Molecular Weight Distribution ◽  
Complex Catalyst ◽  
Good Thermal Stability ◽  
H Nmr ◽  
Catalyst Systems ◽  
C Nmr

Abstract Copolymerization of 5-norbornene-2-metheneoxy-trimethylsilyl [NB-CH2OSi(CH3)3] with norbornene (NB) or methyl 5-norbornene-2-carboxylate (NB-COOCH3) was carried out in toluene by using novel nickel(II) complex catalyst systems, Ni(benzocyclohexan-ketonaphthylimino)2/B(C6F5)3 [Ni(bchkni)2/B(C6F5)3]. The catalyst system showed high activity on the copolymerization of NB-CH2OSi(CH3)3 with NB (2.3–3.3×104 gpolymer/molNi·h) and NB-CH2OSi(CH3)3 with NB-COOCH3(0.5–3.0×104 gpolymer/molNi·h). However, the solubility of copolymers of NB-CH2OSi(CH3)3 with NB and NB-CH2OSi(CH3)3 with NB-COOCH3, which contain 18.7–86.7 mol% of NB-CH2OSi(CH3)3, was too poor to characterize. The achieved copolymers were confirmed to be vinyl-addition copolymers through the analysis of FTIR, 1H NMR, and 13C NMR spectra. The incorporation rate was 8.7–86.7 mol% at a content of 10–90 mol% of the NB-CH2OSi(CH3)3 in the monomer feeds ratios. The obtained ester functionalized NB copolymer containing 8.7–18.7 mol% of NB-CH2OSi(CH3)3 showed a moderate molecular weight (Mw=1.6–6.0×104 g/mol) and relative narrow molecular weight distribution (Mw/Mn=1.6–2.2). Thermogravimetry (TGA) analyses results showed that the copolymers exhibited good thermal stability (Td=330–350°C) and were noncrystalline by WAXD analyses results.

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