Cyclooligomerization of Butadiene and Transition Metal π‐Complexes

Wilke, Günther; Bogdanović, Borislav; Borner, P.; Breil, H.; Hardt, P.; Heimbach, P.; Herrmann, G.; Kaminsky, H.-J.; Keim, W.; Kröner, Michael; Müller, H.; Müller, Ernst Willi; Oberkirch, W.; Schneider, Jörg J.; Stedefeder, J.; Tanaka, K.; Weyer, K.

doi:10.1002/anie.196301051

Cited by 281 publications

(40 citation statements)

References 33 publications

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“…13 The square root dependence was attributed to bimolecular termination, which is typical of freeradical polymerization. This is observed in the polymerization of styrene by Cr(acac) 3 -AlEt 3 system, 27 of ethylene by Cr(acac) 3 -AlEt 3 system, 28 and of methyl Table I. b R p is determined as in Table I.…”

Section: Effect Of Catalyst Concentrationmentioning

confidence: 97%

Investigation of kinetics of 4‐methylpentene‐1 polymerization using Ziegler–Natta‐type catalysts

Balaji

Kothandaraman

Rajarathnam

2003

J of Applied Polymer Sci

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ABSTRACT:The kinetics of 4-methylpentene-1 (4MP1) polymerization by use of Ziegler-Natta-type catalyst systems, M(acac) 3 -AlEt 3 (M ϭ Cr, Mn, Fe, and Co), are investigated in benzene medium at 40°C. The effect of various parameters such as Al/M ratio, reaction time, aging time, temperature, catalyst, and monomer concentrations on the rate of polymerization and yield are examined. The rate of polymerization increased linearly with increasing monomer concentration with first-order dependence, whereas the rate of polymerization with respect to catalyst concentration is found to be 0.5. For all cases, the polymer yield is maximum at an Al/M ratio of 2. The activation energies obtained from linear Arrhenius plots are in the range of 25.27-33.51 kJ mol Ϫ1 . It is found that the aging time to give maximum percentage yield of the polymer varies with the catalyst systems. Based on the experimental results, a plausible mechanism is proposed that envisages a free-radical mechanism. Characterization of the resulting polymer product, for all the cases, through FTIR, 1 H-NMR, and 13 C-NMR studies, showed isomerized polymeric structures with 1,4-structure as dominant.

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Section: Effect Of Catalyst Concentrationmentioning

confidence: 97%

Investigation of kinetics of 4‐methylpentene‐1 polymerization using Ziegler–Natta‐type catalysts

Balaji

Kothandaraman

Rajarathnam

2003

J of Applied Polymer Sci

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“…Isoprene reacts in the presence of various nickel catalysts, and usually provides a complex mixture of dimers and trimers [42,49]. The selectivity can be managed to some extent by choosing an appropriate catalyst (Eq.…”

Section: Cyclodimerization and Cyclotrimerization Of Substituted 13-mentioning

confidence: 99%

Cyclooligomerization and Cycloisomerization of Alkenes and Alkynes

Saito¹

2005

Modern Organonickel Chemistry

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Nickel-catalyzed cyclooligomerization and cycloisomerization reactions of alkenes and alkynes form the cornerstones of organic transition metal chemistry (Reppe, in the 1940s; see Section 6.3.1), and so far these have been among the main subjects studied extensively. In this chapter, nickel-catalyzed cyclooligomerization and cycloisomerization reactions will be described, as will certain nickel-mediated (stoichiometric) reactions, which are closely related to the catalytic reactions. Emphasis is placed on recent developments in nickel chemistry, as earlier studies have been repeatedly reviewed from several viewpoints [1-10]. Cyclization and cycloaddition reactions which involve the addition of other substrates (e.g., hydrosilanes, hydrostannanes and disilanes) will be described in other appropriate chapters in this monograph. 6.1 Cyclooligomerization of AlkenesIn nickel-catalyzed cyclooligomerization reactions of alkenes, strained compounds such as cyclopropenes, methylenecyclopropanes, and norbornadiene are normally used as the reactive substrates. The reactions may involve either the cleavage of the weakened carbon-carbon p bond -as is the case for many cyclooligomerization and cycloisomerization reactions -or the cleavage of the strained carbon-carbon s bond, which is followed by the formation of new carbon-carbon s bonds. Unstrained alkenes usually produce linear oligomers in the presence of nickel catalysts (see Chapter 3).Cyclopropenes are highly strained carbocyclic compounds. For example, the calculated strain energy of cyclopropene is 228 KJ mol À1 (54.5 Kcal mol À1 ) [10]. Accordingly, cyclopropenes are prone to undergo cyclooligomerization in the presence of a Ni catalyst. As an example, 3,3-dimethylcyclopropene provides cyclodimerization and cyclotrimerization products (Eq. (6.1)) [11a, b]. A generally accepted mechanism for this reaction is shown in Scheme 6.1, where the Ni(0) complex interacts with the p bond of the cyclopropene molecule and forms a Ni(0)-h 2 -olefin Modern Organonickel Chemistry. Edited by Y. Tamaru

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“…Other ligands are represented by L but generally are not all identical. (a) Coordination of olefin to rhodium(1 or 111) L4 or GRhI or + olefin L3 or SRhx 01 IIx(olefin) + L (7) (b) Oxidative addition of HC1 to rhodium(1) L4Rhx + HCl e LIRh"'(H)Cl (8) Addition of coordinated hydride or alkyl to co-…”

Section: Characteristic Reactions Of Olefins Coordinated To Rhodiummentioning

confidence: 99%

Transition metal catalysis exemplified by some rhodium-promoted reactions of olefins

Cramer¹

1968

Acc. Chem. Res.

100

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A variety of organic reactions involving olefins, CO, and Hz are catalyzed by solutions of transition metal compounds. Catalysis may be attributed to the ability of the metal ions to coordinate with reactant molecules, thereby both orienting them and reducing the energy barrier for bond making and breaking.Notably, the C-H bond of coordinated molecules when appropriately located with respect to the transition metal is unusually labile. Also, auxiliary ligands, although not ultimately incorporated in the product, may be critically important for catalysis. The rhodium-catalyzed syntheses discussed here (ethylene 4 butene, ethylene + butadiene 4 1,4-hexadienej and 1-butene + isomeric linear butenes) each comprise a characterizing sequence of reversible reaction steps. These steps, which are common to all three syntheses, are: (1) coordination of olefin with Rh(1) or Rh(II1); ( 2 ) oxidative addition of HC1 to Rh(1) to form a Rh(II1) hydride; and (3) addition of coordinated hydride or alkyl to coordinated olefin to give, respectively, a coordinated alkyl or coordinated higher alkyl. In each synthesis system many combinations of these three steps are conceivable. The ability of the catalysts to produce clean products through thermodynamic or kinetic control is discussed for each synthesis.The discoveries of ferrocene and Ziegler catalysts in 1951 awakened interest in the organic chemistry of transition metals. During the fifties most attention was given to the development of these two discoveries. But research of broader implications was also undertaken, including, notably, some very important work characterizing transition metal alkyls, olefin complexes, and related compounds by a group associated with Joseph Chatt. Around 1960 some of the newly organized chemistry was used to explain the cobalt carbonyl catalyzed synthesis of aldehydes from olefins, CO, and Hz. Since then, accelerated by information uncovered by such analytic techniques as infrared, nmr, chromatography, and mass spectroscopy, organotransition metal chemistry has grown expansively. One reason for the interest which led to this growth is that a variety of syntheses, sometimes impressively selective, involving olefins, acetylenes, CO, and Hz are catalyzed by transition metal compounds. These syntheses proceed through, and are understandable in terms of, the chemistry of organometallics, and it is expected (or, at least, hoped) that through increased understanding, catalysts may be designed whose specificity and efficiency will approach those of enzymes.We will be concerned here almost exclusively with the mechanism of reactions of olefins that are catalyzed by compounds of Rh. Focusing on Rh catalysis is not as restrictive as it might appear, because if a compound of one transition metal is effective, generally compounds of other metals can be found which are also catalytically active. Catalysts based on four or more other metals have already been reported for each of the rhodium-promoted reactions described here. Principles of Transition Metal Catalys...

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Cyclooligomerization of Butadiene and Transition Metal π‐Complexes

Cited by 281 publications

References 33 publications

Investigation of kinetics of 4‐methylpentene‐1 polymerization using Ziegler–Natta‐type catalysts

Investigation of kinetics of 4‐methylpentene‐1 polymerization using Ziegler–Natta‐type catalysts

Cyclooligomerization and Cycloisomerization of Alkenes and Alkynes

Transition metal catalysis exemplified by some rhodium-promoted reactions of olefins

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