Metal complexes in catalytic transformation of olefins. 7. Characteristics of active centers and the mechanism of dimerization of ethylene to butene-1 and polymerization of acetylene in the Ti(O-n-Bu)4-AlEt3 catalytic system in ethers

1992 ◽  
Vol 41 (7) ◽  
pp. 1175-1182
Author(s):  
D. B. Furman ◽  
L. N. Russiyan ◽  
V. N. Noskova ◽  
A. P. Lisitskaya ◽  
O. V. Bragin ◽  
...  
Keyword(s):  
Metal Complexes ◽  
Catalytic System ◽  
Catalytic Transformation ◽  
Active Centers

A novel catalytic system for oxygenation with molecular oxygen induced by transition metal complexes with a multidentate N-heterocyclic podand ligand

1996 ◽  
Vol 113 (1-2) ◽  
pp. 117-130 ◽  
Author(s):  
Toshikazu Hirao ◽  
Toshiyuki Moriuchi ◽  
Takuji Ishikawa ◽  
Kouichirou Nishimura ◽  
Satoshi Mikami ◽  
...  
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Molecular Oxygen ◽  
Transition Metal Complexes ◽  
Catalytic System

scholarly journals RADICAL INITIATED COPOLYMERIZATION OF METHYL METHACRYLATE AND ACRYLONITRILE IN PRESENCE OF IRON COMPLEXES

2021 ◽  
Vol 64 (4) ◽  
pp. 34-41
Author(s):  
Ruslan R. Galimullin ◽  
Natalya N. Sigaeva ◽  
Sergey V. Kolesov
Keyword(s):  
Free Radicals ◽  
Nmr Spectroscopy ◽  
Methyl Methacrylate ◽  
Metal Complexes ◽  
1H Nmr Spectroscopy ◽  
Initial Rate ◽  
Iron Complexes ◽  
Active Centers ◽  
Iron Metal ◽  
Effective Constants

This article represents data on the effect of organometallic iron complexes: ferrocene, dicarbonyl dimer of cyclopentadienyl iron and tricarbonyl cyclooctatetraene iron on the copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) initiated by benzoyl peroxide. It is shown that the introduction of metal complexes and their structure affect the initial rate of copolymerization, the form of the diagrams of the composition of the obtained copolymers, and the values of the effective constants of the relative activities of the comonomers in the copolymerization of methyl methacrylate and acrylonitrile (system metallocomplex of iron – peroxide benzoyl: ferrocene – peroxide benzoyl: rММА = 1.58; rАН= 0.08 in 60 °С; rММА = 1.30; rАН = 0.05 in 50 °С; dicarbonyl dimer cyclopentadienyl iron–peroxide benzoyl: rММА = 1.36; rАН = 0.06 in 60 °С; rММА = 1.09; rАН = 0.14 in 50 °С; tricarbonyl cyclooctatetraene iron -peroxide benzoyl: rММА = 1.08; rАН = 0.15 in 60 °С; rММА = 1.14; rАН = 0.05 in 50 °С; peroxide benzoyl: rММА = 1.11; rАН = 0.07 in 60 °С; rММА = 1.11; rАН = 0.07 in 50 °С). The proportions of triadic sequences of units in copolymers, experimentally determined from 1H NMR spectroscopy, are given, as well as the calculated proportions of dyads. The presence of iron metal complexes affects the distribution of the proportions of the triad and dyad sequences of units, as well as their microstructure in copolymers. These changes are explained by the formation of macromolecules, both with the participation of free radicals and the stereospecific coordination active centers of polymerization that are formed in the presence of iron complexes.

scholarly journals Enantiodivergent Non-Linear Effects in Asymmetric Catalysis

2020 ◽  
Author(s):  
Yannick Geiger ◽  
thierry achard ◽  
aline maisse-françois ◽  
Stephane Bellemin-Laponnaz
Keyword(s):  
Metal Complexes ◽  
Asymmetric Catalysis ◽  
Catalytic System ◽  
Catalyst Concentration ◽  
Enantiomeric Excess ◽  
Product Formation ◽  
Experimental Results ◽  
Non Linear ◽  
Linear Effects ◽  
Special Case

In this paper, we theoretically discuss the enantiodivergent product formation in asymmetric catalysis, a process in which the sign of the overall product enantiomer switches upon a change of catalyst concentration. The presented model is based on a catalytic system that consists of both discrete and dimeric aggregated metal complexes, in competition and in equilibrium. These concepts were then expanded to a non-enantiopure catalyst, giving rise to enantiodivergent non-linear effects – a special case of a hyperpositive non-linear effects where the product enantiomer’s sign switches upon a change of the catalyst enantiomeric excess. Different cases are considered allowing a discussion of the influence of the parameters governing both models. Finally, we present experimental results that support the enantiodivergence while varying the concentration of enantiopure catalyst or while varying the enantiomeric excess of the catalyst, using chiral N-methylephedrine as a ligand for the enantioselective addition of dimethylzinc to benzaldehyde.

scholarly journals First experimental evidence for a bis-ethene chromium(I) complex forming from an activated ethene oligomerization catalyst

2020 ◽  
Vol 6 (51) ◽  
pp. eabd7057
Author(s):  
S. Chabbra ◽  
D. M. Smith ◽  
N. L. Bell ◽  
A. J. B. Watson ◽  
M. Bühl ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
Experimental Evidence ◽  
Catalytic System ◽  
Isotope Labeling ◽  
Catalytic Transformation ◽  
Mechanistic Studies ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

A bis-ethene chromium(I) species, which is the postulated key intermediate in the widely accepted metallacyclic mechanism for ethene oligomerization, is experimentally observed. This catalytic transformation is an important commercial route to linear α-olefins (primarily, 1-hexene and 1-octene), which act as comonomers for the production of polyethene. Here, electron paramagnetic resonance studies of a catalytic system based on [Cr(CO)4(PNP)][Al(OC(CF3)3)4] [PNP = Ph2PN(iPr)PPh2] activated with Et6Al2 provide the first unequivocal evidence for a chromium(I) bis-ethene complex. The concentration of this species is enhanced under ethene and isotope labeling studies that confirm its composition as containing [Cr(C2H4)2(CO)2(PNP)]+. These observations open a new route to mechanistic studies of selective ethene oligomerization.

scholarly journals Preparation of Butadiene-Isoprene Copolymer with High Vinyl Contents by Al(OPhCH3)(i-Bu)2/MoO2Cl2∙TNPP

Polymers ◽  
2019 ◽  
Vol 11 (3) ◽  
pp. 527 ◽  
Author(s):  
Peipei Li ◽  
Kai Liu ◽  
Zhe Fu ◽  
Yongliang Yu ◽  
Zhaobo Wang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Monomer Conversion ◽  
Experimental Results ◽  
Reactivity Ratios ◽  
Constant Ratio ◽  
Active Centers ◽  
Coordination Polymerization ◽  
Co Catalyst ◽  
Phenyl Phosphate

In this study, a butadiene-isoprene coordination polymerization was initiated by a binary molybdenum (Mo)-based catalytic system consisting of modified MoO2Cl2 as the primary catalyst, triethyl aluminum substituted by m-cresol as the co-catalyst and tris(nonyl phenyl) phosphate (TNPP) as the ligand. The effects of the amount of catalyst and type of co-catalyst were investigated in detail. Experimental results indicated that when the butadiene-isoprene coordination polymerization was initiated by the binary Mo-based catalytic system, the monomer conversion could reach 90%. The resulting butadiene units were primarily based on 1,2-structures, and the reactivity ratios of butadiene and isoprene were 1.13 and 0.31, respectively. The reaction in the catalytic system was attributed to the non-ideal and non-constant ratio copolymerization. When the addition of isoprene monomers was relatively low, the isoprene units on the butadiene-isoprene copolymers were primarily based on the 1,2- and 3,4-structures. Moreover, the orientation of active centers to 1,2- and 3,4-structures gradually decreased with an increase in the addition of isoprene monomers, which resulted in the generation of high vinyl butadiene-isoprene copolymers.

scholarly journals Enantiodivergent Non-Linear Effects in Asymmetric Catalysis

2020 ◽  
Author(s):  
Yannick Geiger ◽  
thierry achard ◽  
aline maisse-françois ◽  
Stephane Bellemin-Laponnaz
Keyword(s):  
Metal Complexes ◽  
Asymmetric Catalysis ◽  
Catalytic System ◽  
Catalyst Concentration ◽  
Enantiomeric Excess ◽  
Product Formation ◽  
Experimental Results ◽  
Non Linear ◽  
Linear Effects ◽  
Special Case

In this paper, we theoretically discuss the enantiodivergent product formation in asymmetric catalysis, a process in which the sign of the overall product enantiomer switches upon a change of catalyst concentration. The presented model is based on a catalytic system that consists of both discrete and dimeric aggregated metal complexes, in competition and in equilibrium. These concepts were then expanded to a non-enantiopure catalyst, giving rise to enantiodivergent non-linear effects – a special case of a hyperpositive non-linear effects where the product enantiomer’s sign switches upon a change of the catalyst enantiomeric excess. Different cases are considered allowing a discussion of the influence of the parameters governing both models. Finally, we present experimental results that support the enantiodivergence while varying the concentration of enantiopure catalyst or while varying the enantiomeric excess of the catalyst, using chiral N-methylephedrine as a ligand for the enantioselective addition of dimethylzinc to benzaldehyde.

scholarly journals Enantiodivergent Non-Linear Effects in Asymmetric Catalysis

2020 ◽  
Author(s):  
Yannick Geiger ◽  
thierry achard ◽  
aline maisse-françois ◽  
Stephane Bellemin-Laponnaz
Keyword(s):  
Metal Complexes ◽  
Asymmetric Catalysis ◽  
Catalytic System ◽  
Catalyst Concentration ◽  
Enantiomeric Excess ◽  
Product Formation ◽  
Experimental Results ◽  
Non Linear ◽  
Linear Effects ◽  
Special Case

In this paper, we theoretically discuss the enantiodivergent product formation in asymmetric catalysis, a process in which the sign of the overall product enantiomer switches upon a change of catalyst concentration. The presented model is based on a catalytic system that consists of both discrete and dimeric aggregated metal complexes, in competition and in equilibrium. These concepts were then expanded to a non-enantiopure catalyst, giving rise to enantiodivergent non-linear effects – a special case of a hyperpositive non-linear effects where the product enantiomer’s sign switches upon a change of the catalyst enantiomeric excess. Different cases are considered allowing a discussion of the influence of the parameters governing both models. Finally, we present experimental results that support the enantiodivergence while varying the concentration of enantiopure catalyst or while varying the enantiomeric excess of the catalyst, using chiral N-methylephedrine as a ligand for the enantioselective addition of dimethylzinc to benzaldehyde.

Übergangsmetallkomplexe mit Schwefelliganden, XCl+ Fell-Komplexe des fünfzähnigen Thioether-Thiolat-Aminliganden ′buNHS4′-H2: Synthese, Charakterisierung, Reaktivität und Stereochemie (′buNHS4′-H2 = 2,2′-Bis(2-mercapto-3,5-di-tertiärbutyl-phenylthio)diethylamin) / Transition Metal Complexes with Sulfur Ligands, XCI+ Fell Complexes of the Pentadentate Thioether-Thiolate-Amine Ligand ′buNHS4′-H2: Synthesis, Characterization, Reactivity and Stereochemistry (′buNHS4′-H2 = 2,2′-Bis(2-mercapto-3,5-di-tertiarybutyl-phenylthio)diethylamine)

1992 ◽  
Vol 47 (8) ◽  
pp. 1105-1114 ◽  
Author(s):  
Dieter Sellmann ◽  
Wolfgang Soglowek ◽  
Matthias Moll
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Low Temperatures ◽  
Positional Isomers ◽  
Model Compounds ◽  
Active Centers ◽  
High Spin Complex ◽  
Amine Ligand ◽  
Spin Complex

In search of model compounds for the active centers of nitrogenases, [Fe(L)(′buNHS4')] complexes of the pentadentate thioether-thiolate-amine ligand ′buNHS4'2- (′buNHS4'-H2 = 2,2′-bis(2-mercapto-3,5-di-tertiarybutyl-phenylthio)diethylamine) were obtained.Alkylation of′buS2'-H2 with (BrC2H4)2NH yielded the new ligand ′buNHS4'-H2 as a mixture of positional isomers. Isolation of single isomers was achieved by reacting the mixture with FecL2•4H2O and CO in order to give the corresponding [Fe(CO)] complexes which were separated and hydrolyzed to yield the free ligands.Reaction of'buNHS4'-H2 with FeCl2•4H2O led to the high-spin complex [Fe(′buNHS4')] which is extremely air-sensitive in solution. It rapidly reacts with L = CO, NO, PMe3, and N2H4, and is the most suitable starting material for syntheses of [Fe(L)(′buNHS4')] complexes which were characterized for L = CO, NO+, NO, PMe3 and N2H4. All complexes are considerably better soluble in organic solvents than the corresponding parent compounds [Fe(L)(′NHS4')], (′NHS4'-H2 = 2,2′-bis(2-mercaptophenylthio)diethylamine), but have similar properties in most other respects. In the oxidation of [Fe(N2H4)(′buNHS4')] at low temperatures, there is evidence for the formation of the diazene complex [μ-N2H2{Fe(′buNHS4')}2].

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