A new allene hexamer

Scholten, J. P.; Ploeg, H. J. Van Der

doi:10.1016/s0040-4039(01)84720-1

Cited by 16 publications

(6 citation statements)

References 7 publications

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“…The polymerization catalyzed with Rh complexes has been studied from the end of the 1960's, when it was found that this reaction can give high-molecular- [15][16][17][18] or cyclooligomers [19][20][21][22] or both, depending on the ligands of the Rh complex and the reaction conditions. The Rh(I) complexes containing Cl and CO ligands and no or only one PPh 3 ligand were found to give crystalline (i.e., regular) polymers together with small amounts of cyclooligomers, which can be removed by dissolving in acetone 16,17 .…”

Section: Propadiene (Allene) and Substituted Propadienesmentioning

confidence: 99%

“…Rhodium complexes involving more than one PPh 3 ligand, such as [RhCl(CO) 2 (PPh 3 ) 2 ], [RhCl(CH 2 =CH 2 ) 2 (PPh 3 ) 2 ] and [RhCl(PPh 3 ) 3 ], are inactive in the polymerization but active in the cyclooligomerization of propadiene 16,[19][20][21][22] . Evidently, the reactivity of these complexes is not limited by steric factors, because other complexes with even more crowded central Rh atom polymerize substituted propadienes.…”

Section: Propadiene (Allene) and Substituted Propadienesmentioning

confidence: 99%

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Controlled and Living Polymerizations Induced with Rhodium Catalysts. A Review

Sedláček¹,

Vohlı́dal²

2003

Collect. Czech. Chem. Commun.

100

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In the last fifteen years, a large variety of specialty polymers of diverse chemical structure and functionality have been synthesized with the rhodium-based catalysts. The high tolerance to the reaction medium and functional groups of monomers, as well as ability to control various structure features of the polymer formed are typical properties of these catalysts. In addition, some rhodium catalysts can be anchored to inorganic or organic supports or dissolved in ionic liquids to form heterophase polymerization systems, which opens the way to pure, well-defined polymers free of the catalyst residues, as well as to recycling rhodium catalysts. This review provides a survey on the polymerization reactions induced with rhodium-based catalysts, in which one or more structure attributes of the polymer formed are subject to control. The structure attributes considered are (i) sequential arrangement of monomeric units along polymer chains; (ii) head-tail isomerism of polymer molecules; (iii) configurational structure of polymer molecules; (iv) conformation of polymer molecules; and (v) molecular weight and molecular-weight distribution of the polymer formed. A review with 188 references.

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Section: Propadiene (Allene) and Substituted Propadienesmentioning

confidence: 99%

Section: Propadiene (Allene) and Substituted Propadienesmentioning

confidence: 99%

Controlled and Living Polymerizations Induced with Rhodium Catalysts. A Review

Sedláček¹,

Vohlı́dal²

2003

Collect. Czech. Chem. Commun.

100

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“…Rh(I) complexes catalyze polymerization or cyclooligomerization of 1,2-dienes depending on auxiliary ligands of the complexes and reaction conditions. Catalysts such as RhCl(PPh 3 ) 3 , [RhCl(CH 2 CH 2 ) 2 ] 2 −PPh 3 mixture, and [RhCl(CO) 2 ] 2 −PPh 3 mixture lead to cyclooligomerization of 1,2-propadiene …”

Section: Introductionmentioning

confidence: 99%

Rhodium(I) Complexes with π-Coordinated Arylallene. Structures in the Solid State and in Solution and Reaction with Arylallene To Give Rhodacyclopentane

et al. 1998

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Reactions of phenylallene and of (4-fluorophenyl)allene with [Rh(μ-Cl)(PMe3)2]2 (Rh:arylallene = 1:1) give Rh(I) complexes with π-coordinated arylallene, RhCl(η2-CH2CCHAr)(PMe3)2 (1a, Ar = C6H5; 1b, Ar = C6H4F-p). X-ray crystallography of 1a,b has established their square-planar coordination around the rhodium center, which is bonded to the 2,3-double bond of the arylallene. The aryl group of the ligand and the Rh center are situated on the same side of the uncoordinated 1,2-double bond. The position of an ortho hydrogen of the phenyl group in the ligand suggests an agostic interaction between the C−H group and the Rh center. Dissolution of 1a in benzene results in equilibration with its isomer 3a, which does not have a close contact between the ortho C−H group of the ligand and the Rh center. The 1H NMR spectra of an equilibrated mixture in the temperature range 30−55 °C afford thermodynamic parameters for 3a↔1a of ΔH° = −5.0 kJ mol-1 and ΔS° = −8 J mol-1 K-1. The arylallenes react also with RhCl(PMe3)3 in a 1.2:1 molar ratio to yield pentacoordinated Rh(I)−arylallene complexes, RhCl(η2-CH2CCHAr)(PMe3)3 (2a, Ar = C6H5; 2b, Ar = C6H4F-p). A crystallographic study of 2b shows a distorted trigonal-bipyramidal coordination around the Rh center, which is bonded to equatorial Cl, PMe3, and 2,3-η2-CH2CCHAr ligands and to two apical PMe3 ligands. The 4-fluorophenyl group of the ligand and the Rh center are situated on opposite sides of the uncoordinated CC double bond. Complex 2a is in equilibrium with its isomer 4a, which shows dynamic NMR behavior on the NMR time scale. Reactions in a 3:1 molar ratio give rhodacyclopentanes, Ar = C6H5; 5b, Ar = C6H4F-p) as the main product. Complex 5a is also obtained from reaction of phenylallene with 2a. Reactions of (4-fluorophenyl)allene with RhCl(PEt3)3, RhCl{P(i-Pr)3}2, and RhCl(PPh3)3 proceed smoothly to give the corresponding Rh(I)−(4-fluorophenyl)allene complexes, RhCl(η2-CH2CCHC6H4F-p)(PR3)2 (6, R = Et; 7, R = i-Pr; 8, R = Ph). The 1H NMR spectra of the complexes and X-ray crystallography of 8 indicate square-planar coordination around the Rh center, which is bonded to the 2,3-double bond of the arylallene.

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“…In cases of carboxylate ligands ( 1a − 1c ), the increase of the electron-withdrawing character of the anionic ligand tends to increase the content of the 1,2-polymerization unit. Since the electron-accepting ability of halide ligands coordinated to the nickel(II) has been reported in the order Cl < Br < I, the content of the 1,2-polymerization unit might be expected to be in the order Cl < Br < I. Although we have done our best to purify allyl halides used for the catalyst preparation by distilling them just before use, in particular, the purity of allyl iodide might not be sufficient enough.…”

Section: Resultsmentioning

confidence: 99%

Living Coordination Polymerization of Alkoxyallenes by π-Allylnickel Catalyst. 2. Effect of Anionic Ligands on Polymerization Behavior and Polymer Structure

et al. 1998

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The coordination polymerization of (n-octyloxy)allene (2) was carried out by π-allylnickel catalysts possessing various carboxylate ligands (1a−1c). The electronic character of the carboxylate ligand strongly influences the polymerization. Electron-withdrawing groups provide a living system that produces polymers with well-defined molecular weights and narrow molecular weight distributions in high yields. Without electron-withdrawing substituents, the reaction produces oligomeric byproducts. The ratio of 1,2- to 2,3-polymerization unit in the polymer increased with the electron-withdrawing character of carboxylate ligands. π-Allylnickel catalysts bearing halide ligands (1d, 1e, and 1f/Na2S2O3) also gave polymers from 2 in high yields, in which the polymerization rate, the microstructure, and the molecular weight distributions (M w/M n) of polymers were dependent upon the specific halide. The catalyst with chloride (1d) afforded a polymer with narrow M w/M n (1.03), possessing the ratio of 1,2- to 2,3-polymerization unit of 6:94, whereas with iodide (1f/Na2S2O3), the polymerization took place much faster to give a polymer (1,2-:2,3-polymerization unit = 16:84) with a little broader M w/M n (1.10).

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A new allene hexamer

Cited by 16 publications

References 7 publications

Controlled and Living Polymerizations Induced with Rhodium Catalysts. A Review

Controlled and Living Polymerizations Induced with Rhodium Catalysts. A Review

Rhodium(I) Complexes with π-Coordinated Arylallene. Structures in the Solid State and in Solution and Reaction with Arylallene To Give Rhodacyclopentane

Living Coordination Polymerization of Alkoxyallenes by π-Allylnickel Catalyst. 2. Effect of Anionic Ligands on Polymerization Behavior and Polymer Structure

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