Stereospecificity of Alkaline Earth Metal Compounds in the Anionic Polymerization of N,N-Dimethylacrylamide

Nakhmanovich, B. I.; Urman, Yakov G.; Arest-Yakubovich, A. A.

doi:10.1002/1521-3935(20010501)202:8<1327::aid-macp1327>3.0.co;2-w

Cited by 10 publications

(10 citation statements)

References 7 publications

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“…It is well known that n-butyllithium deprotonates THF at room temperature, the anion then decomposed to give butane, ethylene and the lithium enolate of acetaldehyde [14]. Mixed complexes of the general formula [RLi:LiOR] have long been known and alkoxides have a large effect on the reactivity of organolithium compounds [17].…”

Section: Effect Of Alkoxidessupporting

confidence: 75%

“…Besides derivatives of alkali metals, various alkaline earth metal compounds, including metal alkyls and bimetallic metal-aluminium complexes, were also found to be reactive initiators for DMAAm polymerization. These initiators usually produce polymer quantitatively within a few minutes, if not seconds [14].…”

Section: Liquid Adsorption Chromatography Under Critical Conditionsmentioning

confidence: 99%

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Anionic polymerization of N,N-dimethylacrylamide with thienyllithium and synthesis of block co-polymers of isobutylene and N,N-dimethylacrylamide by site transformation of chain ends

Martínez-Castro¹,

Zhang²,

Pergushov³

et al. 2006

Designed Monomers and Polymers

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The anionic polymerization of N,N-dimethylacrylamide (DMAAm) was carried out in THF with a binary initiator system prepared from thienyllithium and the Lewis acids triethylaluminium (Et 3 Al), diethylzinc (Et 2 Zn) or triethylborane (Et 3 B). Polymerizations proceeded in a homogeneous manner and gave polymers having controlled molecular weights. However, in presence of alkoxides the polymerization resulted in polymers insoluble in THF, even when using Et 3 Al. A synthetic route for the synthesis of polyisobutylene-b-PDMAAm was developed by combining living carbocationic and anionic polymerizations. Thiophene end-capped polyisobutylene (PIB-T), prepared by cationic polymerization, was metalated with n-butyllithium in THF at −40 • C. The resulting stable macrocarbanion (PIB-T − , Li + ), in conjunction with Lewis acids, was used to initiate the living anionic polymerization of DMAAm, resulting in a new amphiphilic block co-polymer PIB-b-PDMAAm. The molecular structure was characterized by size exclusion and adsorption chromatography and NMR, and the micellisation in aqueous solution was characterized by fluorometry and dynamic light scattering.

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Section: Effect Of Alkoxidessupporting

confidence: 75%

Section: Liquid Adsorption Chromatography Under Critical Conditionsmentioning

confidence: 99%

Anionic polymerization of N,N-dimethylacrylamide with thienyllithium and synthesis of block co-polymers of isobutylene and N,N-dimethylacrylamide by site transformation of chain ends

Martínez-Castro¹,

Zhang²,

Pergushov³

et al. 2006

Designed Monomers and Polymers

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“…In nonpolar solvents, such as toluene, such intramolecular complexation should predominate, affecting both the reactivity of active chain ends and, possibly, the microtacticity of the obtained polymers. For the anionic polymerization of DMAAm by dibutylmagnesium, it was found that the isotactic triad content is almost the same in THF and toluene . This contradicts earlier data that a lower dielectric constant of the medium leads to higher isotacticity of PDMAAm synthesized by anionic polymerization from organometallic compounds of both alkali and alkaline earth metals .…”

Section: Introductioncontrasting

confidence: 56%

Section: Introductionmentioning

confidence: 99%

“…For all these applications, it is very important to control structural and molecular weight characteristics of PDMAAm, and the most reliable approach in this respect is anionic polymerization of N,N-dimethylacrylamide (DMAAm). It is known that the anionic polymerization of DMAAm by organolithium initiators in both hydrocarbons 8 and THF [9][10][11] is not well controlled, even in the presence of σ-donor additives, such as TMEDA, 11 due to formation of insoluble, highly crystalline polymers with highly isotactic microstructure. 8-10,12,13,14a Recently, to control the polymerization of DMAAm, new effective anionic initiating systems were developed, consisting of organometallic compounds of alkali and alkaline earth metals modified by electron acceptor Lewis acids (LA), such as Et 3 B, 10a,14b Et 2 Zn, 10,12,13,14b and Et 3 Al.…”

Section: Introductionmentioning

confidence: 99%

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Quantum-Chemical Study of the Effect of Triethylaluminum on the Chain-End Structure, Reactivity, and Microtacticity of Poly(N,N-dimethylacrylamide) with Lithium Counterion in Nonpolar Solvents

Yakimansky

Müller

2010

Macromolecules

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Reactions of chain growth in the anionic polymerization of N,N-dimethylacrylamide (DMAAm) with lithium counterion in the presence of triethylaluminum (Et3Al) were studied using quantum-chemical DFT methods. The active sites were simulated by chain fragments consisting of two DMAAm units, the lithium counterion being coordinated to carbonyl oxygen atoms of both ultimate and penultimate units. For all local minima and transition states zero-point vibration energies and free energies, ΔG, at 200 K were calculated. It was shown that in the absence of Et3Al iso-addition of the monomer to the model chain end is the most favorable, while in the presence of two Et3Al molecules syndio- and iso-additions of DMAAm are equally probable. In the presence of one Et3Al molecule, an unambiguous prediction of the prevailing stereomode of DMAAm addition is impossible because different stereomodes are preferred at the BHLYP/SVP (syndio-addition via 1LA-DAS mechanism) and BHLYP/aug-cc-pVTZ//BHLYP/SVP (iso-addition via 1LA-AM mechanism) levels. Thus, on the basis of the performed DFT calculations, it is possible to predict the possibility to influence the microtacticity of poly(N,N-dimethylacrylamide), varying the [Al]/[Li] ratio: the polymer should be predominantly isotactic at [Al]/[Li] = 0 and atactic at [Al]/[Li] ≥ 2.

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Aktivierung einer an Zink gebundenen Ethylgruppe durch Bildung eines Zn‐C_Et‐Ba‐Fragments und Kristallstruktur von [((Me₃Si)₂N)Ba(thf)Zn₂(μ‐Et)(μ₃‐PSitBu₃)₂]₂ mit verbrückenden Ethyl‐Substituenten

2005

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Die metallorganische Chemie der schweren Erdalkalimetalle wird seit vielen Jahrzehnten erforscht. Trotz enormer Anstrengungen, solche Verbindungen herzustellen und strukturell zu charakterisieren, sind jedoch nur wenige Kristallstrukturen von bariumorganischen Verbindungen bekannt. Bereits vor mehr als 60 Jahren berichteten Gilman und Woods, dass die Zugabe von Diethylzink zu einer stark erhöhten Reaktivität von Dialkylbarium gegenüber Benzonitril führt.[1] Bis heute blieben diese bariumorganischen Verbindungen jedoch schlecht charakterisiert, vor allem wegen ihrer Schwerlös-lichkeit in gängigen organischen Lösungsmitteln (stark ionische Metall-Kohlenstoff-Bindung), niedrigen Ausbeuten (Nebenreaktionen, Notwendigkeit der Metallaktivierung vor der Reaktion), geringen Reinheit und wegen Reaktionen mit dem Lösungsmittel (Etherspaltungen). In den letzten Jahrzehnten wurden mehrere Herstellungsmethoden entwickelt, um s-gebundene Alkylbarium-Verbindungen zu synthetisieren, [2] und die meisten dieser Derivate enthalten a-gebundene Aryl- [3] und Trialkylsilyl-Gruppen.[4] Diese Verbindungen fanden breite Anwendung als Polymerisationsinitiatoren, [5] ihre Strukturen konnten aber erst in jüngster Zeit bestimmt werden. [6,7] Um Nebenreaktionen zu vermeiden, tragen die Substituenten keine b-Wasserstoffatome. Außerdem wurde für lösungsmittelfreies monomeres Dimethylbarium gemäß Ab-initio-Rechnungen eine gewinkelte Struktur vorhergesagt.[ (Transmetallierungsreaktion). Wird die Metallierungsreaktion in Toluol und ohne überschüssiges THF durchgeführt, muss sich das Bariumatom intramolekular sterisch absättigen, sodass die Reaktion von 1 (R = Me, Et) mit [(thf)Ba(N(SiMe 3 ) 2 ) 2 ] 2 zur Verbindung 3 führt (Schema 1). Der Hauptunterschied zwischen diesen Reaktionen liegt darin, dass bei der Synthese von 2 alle Bis(trimethylsilyl)amido-Gruppen als Deprotonierungsmittel reagieren, während bei der Bildung von 3 zwei Ethyl-und zwei Amidogruppen die Phosphanide deprotonieren. Diese Beobachtung kann durch eine Aktivierung der Ethyl-Substituenten vor der Reaktion erklärt werden. Demnach aktivieren Ba-C Et -Zn-Dreizentren-Zweielektronen-Bindungen oder agostische Wechselwirkungen zwischen C-H-s-Bindungen und dem Bariumkation, so wie in 3, die Ethylgruppe. Anders als bei der Reaktion in Toluol gibt es keine Notwendigkeit für das Auftreten solcher Bindungen in 2, weil bei einer Reaktionsführung in THF das Bariumatom durch Lösungsmittelmole-küle koordinativ immer abgesättigt bleibt.Während in 2 die verzerrt oktaedrische Koordinationssphäre des Bariums durch vier THF-Moleküle vervollständigt Schema 1.

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Stereospecificity of Alkaline Earth Metal Compounds in the Anionic Polymerization of N,N-Dimethylacrylamide

Cited by 10 publications

References 7 publications

Anionic polymerization of N,N-dimethylacrylamide with thienyllithium and synthesis of block co-polymers of isobutylene and N,N-dimethylacrylamide by site transformation of chain ends

Anionic polymerization of N,N-dimethylacrylamide with thienyllithium and synthesis of block co-polymers of isobutylene and N,N-dimethylacrylamide by site transformation of chain ends

Quantum-Chemical Study of the Effect of Triethylaluminum on the Chain-End Structure, Reactivity, and Microtacticity of Poly(N,N-dimethylacrylamide) with Lithium Counterion in Nonpolar Solvents

Aktivierung einer an Zink gebundenen Ethylgruppe durch Bildung eines Zn‐C_Et‐Ba‐Fragments und Kristallstruktur von [((Me₃Si)₂N)Ba(thf)Zn₂(μ‐Et)(μ₃‐PSitBu₃)₂]₂ mit verbrückenden Ethyl‐Substituenten

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Stereospecificity of Alkaline Earth Metal Compounds in the Anionic Polymerization of N,N-Dimethylacrylamide

Cited by 10 publications

References 7 publications

Anionic polymerization of N,N-dimethylacrylamide with thienyllithium and synthesis of block co-polymers of isobutylene and N,N-dimethylacrylamide by site transformation of chain ends

Anionic polymerization of N,N-dimethylacrylamide with thienyllithium and synthesis of block co-polymers of isobutylene and N,N-dimethylacrylamide by site transformation of chain ends

Quantum-Chemical Study of the Effect of Triethylaluminum on the Chain-End Structure, Reactivity, and Microtacticity of Poly(N,N-dimethylacrylamide) with Lithium Counterion in Nonpolar Solvents

Aktivierung einer an Zink gebundenen Ethylgruppe durch Bildung eines Zn‐CEt‐Ba‐Fragments und Kristallstruktur von [((Me3Si)2N)Ba(thf)Zn2(μ‐Et)(μ3‐PSitBu3)2]2 mit verbrückenden Ethyl‐Substituenten

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Aktivierung einer an Zink gebundenen Ethylgruppe durch Bildung eines Zn‐C_Et‐Ba‐Fragments und Kristallstruktur von [((Me₃Si)₂N)Ba(thf)Zn₂(μ‐Et)(μ₃‐PSitBu₃)₂]₂ mit verbrückenden Ethyl‐Substituenten