New ionic half-metallocenes of early lanthanides

Visseaux, Marc; Zinck, Philippe; Terrier, Michael; Mortreux, André; Roussel, Pascal

doi:10.1016/j.jallcom.2007.04.140

Cited by 27 publications

(27 citation statements)

References 29 publications

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“…Visseaux reported an elegant alternative method of “borohydride/alkyl (B/A) route” for preparing half‐sandwich based early lanthanide catalysts, which showed similar efficiencies as their neutral homologues . Two anionic (Cp′)Nd(BH 4 ) 3 species and one cationic Mg(THF) 6 (Cp′=C 5 Me 5 , 85 ; Cp′=C 5 H 5 , 86 ; Cp′=C 5 H 2 Ph 3 , 87 ) were synthesized, with high trans ‐1,4‐regularity (98.2 %), and controllable polymerization capability.…”

Section: Stereoselective Polymerization Of Conjugated Dienessupporting

confidence: 75%

Precisely Controlled Polymerization of Styrene and Conjugated Dienes by Group 3 Single‐Site Catalysts

et al. 2017

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This Review aims at a comprehensive overview on the recent stereospecific control polymerizations by group 3 metal complexes based catalytic systems in combination with aluminum alkyls and organoborates etc. co‐catalysts. The involved monomers include styrene and substituted styrenes, and the conjugated dienes like isoprene and butadiene, and their derivatives. The syndio‐ and iso‐selective polymerizations of styrene, unmasked polar styrenes and the copolymerizations of styrene with conjugated dienes and polar styrenes are summarized. The factors of influencing the catalytic activity and selectivity are discussed. The regio‐ and stereo‐ selective polymerizations of conjugated dienes, polar diene derivatives and their copolymerizations are reviewed. The relationship between catalyst structure and polymerization activity, the mechanism of stereo‐selective polymerization and the influence of different cocatalysts are discussed.

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Section: Stereoselective Polymerization Of Conjugated Dienessupporting

confidence: 75%

Precisely Controlled Polymerization of Styrene and Conjugated Dienes by Group 3 Single‐Site Catalysts

et al. 2017

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Section: Resultsmentioning

confidence: 99%

“…Complexes 1 , 2 , and 3 were synthesized by ionic metathesis, according to published procedures,16a–c whereas complex 4 was prepared by using the “borohydride alkyl route,” as previously reported by our group 16d. All of these half‐sandwich complexes are active and selective preinitiators towards isoprene polymerization, and lead to either highly cis ‐ (with 1 16a) or trans ‐1,4‐ (with 2, 6a 3 [16c] or 4 16d) polyisoprenes. In this context, one could expect catalysts based on 2 , 3 , and 4 to insert α‐olefin comonomers into the trans ‐1,4‐polyisoprene structure, because catalysts able to statistically copolymerize diene and α‐olefin mainly give rise to a trans ‐1,4‐arrangement of diene units in the copolymer produced 5d.…”

Section: Resultsmentioning

confidence: 99%

A Joint Experimental/Theoretical Investigation of the Statistical Olefin/Conjugated Diene Copolymerization Catalyzed by a Hemi‐Lanthanidocene [(Cp*)(BH₄)LnR]

Perrin

Bonnet

Chenal

et al. 2010

Chemistry A European J

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Statistical copolymerization of ethylene and isoprene was achieved by using a borohydrido half-lanthanidocene complex. Under copolymerization conditions, activation of [(Cp*)(BH(4))(2)Nd(thf)(2)] (Cp*=η(5)-C(5)Me(5)) by an appropriate alkylating agent affords trans-1,4-poly-isoprene-co-ethylene. Analysis of the microstructure of the copolymer revealed the presence of successive short sequences of ethylene/ethylene, trans-1,4-isoprene/ethylene, and trans-1,4-isoprene/trans-1,4-isoprene. A small amount of 1,2-insertion of isoprene was observed, and no cyclic structures within the chain were characterized. Test runs showed that these catalysts are unable to copolymerize α-olefins (such as hex-1-ene) with isoprene. The probable initial steps in the copolymerization have been computed at the DFT level of theory. Analysis of the energy profile provides insight into the catalyst's activity and selectivity. Our theoretical results highlight the key role played by the allyl intermediate, in which diene insertion, and to a lesser extent olefin insertion, is the rate-determining step of the process. These results also illustrate the coordination behavior of the allyl ligand during the insertion of an incoming monomer, which directly inserts, after pre-coordination to the metal center, into the η(3)-allyl ligand without inducing an η(3) to η(1) haptotropic shift. Finally, the inactivity of this family of catalysts towards the copolymerization of hex-1-ene was rationalized on the basis of the free-energy profile of the copolymerization.

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“…When 1b is synthesized in situ, 32 3 combination yielded more than 90% cispolyisoprene, but the activity was significantly lower than with trityl borate as activator. 36 The comparison of the results presented in Table 2 3 , whereas 2b does.…”

Section: 9)mentioning

confidence: 94%

Tuning the catalytic properties of rare earth borohydrides for the polymerisation of isoprene

et al. 2013

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Previous results obtained for the cis-polymerisation of isoprene with scandium half-sandwich complex Cp*Sc(BH 4 ) 2 (THF) 1a were extended to its neodymium analog. The X-ray structure of the already reported neodymium monomer compound Cp*Nd(BH 4 ) 2 (THF) 2 1b is presented. Cp*Nd(BH 4 ) 2 (THF) 2 /[CPh 3 ]-[B(C 6 F 5 ) 4 ]/Al( i Bu) 3 catalytic system was found to be very active and stereoselective towards isoprene polymerisation, leading to highly 1,4-cis polyisoprene up to 92%. The effect on isoprene polymerisation of the addition of a NHC molecule to Cp*Ln(BH 4 ) 2 (THF) n pre-catalyst (Cp* = η 5 -C 5 Me 5 , Ln = Sc, n = 1, 1a; Nd, n = 2, 1b; Sm, n = 2, 1c) or to a trisborohydride Ln(BH 4 ) 3 (THF) n (Ln = Sc, n = 1.5, 2a; Nd, n = 3, 2b; Sm, n = 3, 2c) was also studied. Several NHC ligands were assessed: the classical [1-C{(N t BuCH)} 2 ] (L 1 ) and functional N-heterocyclic carbenes, two amino-tethered HNBu t CH 2 CH 2 [1-C{N(CHCH)NR}] (HL 2-R ) (R = t Bu, Mes (Mes = 2,4,6-Me 3 -C 6 H 2 )) and the hydroxyl-tethered HOCMe 2 CH 2 [1-C{N(CHCH)N i Pr}] (HL 3 ). Neodymiumbased complex (L 2-tBu )Nd(BH 4 ) 2 (THF) 2 3 could be isolated and characterized. With some of the catalytic combinations tested, the introduction of the NHC ligand in the coordination sphere of the complex induces a switch of the stereoselectivity of the resulting polymer. Scandium complex 2a, which produces mainly 1,4-cis polyisoprene when associated to a borate activator and aluminum alkyl, leads to 1,4-trans polymer up to 94% regular when HL 2-tBu carbene is added to the same reaction mixture. This result is the only example of highly trans-polyisoprene synthesized with a scandium based catalyst. Coordination of the carbene moiety to the rare earth centre is confirmed by NMR studies on paramagnetic neodymium pre-catalysts.

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New ionic half-metallocenes of early lanthanides

Cited by 27 publications

References 29 publications

Precisely Controlled Polymerization of Styrene and Conjugated Dienes by Group 3 Single‐Site Catalysts

Precisely Controlled Polymerization of Styrene and Conjugated Dienes by Group 3 Single‐Site Catalysts

A Joint Experimental/Theoretical Investigation of the Statistical Olefin/Conjugated Diene Copolymerization Catalyzed by a Hemi‐Lanthanidocene [(Cp*)(BH₄)LnR]

Tuning the catalytic properties of rare earth borohydrides for the polymerisation of isoprene

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New ionic half-metallocenes of early lanthanides

Cited by 27 publications

References 29 publications

Precisely Controlled Polymerization of Styrene and Conjugated Dienes by Group 3 Single‐Site Catalysts

Precisely Controlled Polymerization of Styrene and Conjugated Dienes by Group 3 Single‐Site Catalysts

A Joint Experimental/Theoretical Investigation of the Statistical Olefin/Conjugated Diene Copolymerization Catalyzed by a Hemi‐Lanthanidocene [(Cp*)(BH4)LnR]

Tuning the catalytic properties of rare earth borohydrides for the polymerisation of isoprene

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A Joint Experimental/Theoretical Investigation of the Statistical Olefin/Conjugated Diene Copolymerization Catalyzed by a Hemi‐Lanthanidocene [(Cp*)(BH₄)LnR]