Reactions of ε-Caprolactone with (Alkyne)zirconocene Complexes: Investigation of Elemental Steps in Catalytic Ring-Opening Polymerization of Lactones

Thomas, Dominique; Arndt, Perdita; Peulecke, Normen; Spannenberg, Anke; Kempe, Rhett; Rosenthal, Uwe

doi:10.1002/(sici)1099-0682(199809)1998:9<1351::aid-ejic1351>3.0.co;2-n

Cited by 30 publications

(27 citation statements)

References 34 publications

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“…This is consistent with the results we obtained in the case of (alkyne)zirconocene catalysts (for propagation and termination)12 and those obtained by other groups in monitoring lactone polymerization by NMR spectroscopy 10b. Furthermore, no end‐group signals were found 12. This has been explained in other reports by the formation of a cyclic polymer as the termination step 10a,10d.…”

Section: Resultssupporting

confidence: 92%

“…The corresponding heterobimetallic zirconocene(alkyne)/aluminium derivatives ( 3 , 4 ) (Table 3, runs 5, 7) show no significant changes in comparison to their monometallic example in the ROP. The NMR investigation of the ROP of ϵ‐caprolactone with initiator 4 shows the formation of a five‐membered metallacyclic spiro‐zirconadihydrofuran complex, which was already described as the first step in the ROP of lactones by the monometallic (zirconocene) alkyne complexes;12 it is followed by a rapid polymerization. No influence of the HAl( i Bu) 2 was found.…”

Section: Resultsmentioning

confidence: 93%

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Bimetallic Titanocene or Zirconocene/Aluminium Complexes as Active Catalysts in Lactone Polymerization Reactions

Arndt

Spannenberg

Baumann

et al. 2001

Eur. J. Inorg. Chem.

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The metallocene alkyne complexes [Cp 2 M(L)(η 2 -Me 3 SiC 2 R)] react with diisobutylaluminium hydride at room temp. by addition of HAl(iBu) 2 to yield the heterobimetallic complexes [{Cp 2 M}(µ-η 1 :η 2 -RCCSiMe 3 )(µ-H){Al(iBu) 2 }] [{Cp 2 M}: (η 5 -C 5 H 5 ) 2 Ti, R = Ph 1, R = SiMe 3 2; {Cp 2 M}: (η 5 -C 5 H 5 ) 2 Zr, R = SiMe 3 3; {Cp 2 M}: (ebthi)Zr, R = SiMe 3 4] {ebthi: rac-[1,2-ethylene-1,1Ј-bis(η 5 -tetrahydroindenyl)]}. Complexes 1−4

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 93%

Bimetallic Titanocene or Zirconocene/Aluminium Complexes as Active Catalysts in Lactone Polymerization Reactions

Arndt

Spannenberg

Baumann

et al. 2001

Eur. J. Inorg. Chem.

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“…It also exemplifies the primary step of a dissociative mechanism which has been proposed for various reactions of titanocene−BTMSA complexes with σ-electron donors or acetylenes on the basis of reaction intermediates or products . In contrast, zirconocene−BTMSA complexes react currently by an associative mechanism, probably due to a larger atom diameter and a higher electropositivity of zirconium . On the other hand, these properties may make the preparation and isolation of zirconocene yet more difficult.…”

Section: Discussionmentioning

confidence: 79%

Bis[η⁵-tetramethyl(trimethylsilyl)cyclopentadienyl]titanium(II) and Its π-Complexes with Bis(trimethylsilyl)acetylene and Ethylene

et al. 1999

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Thermally induced elimination of bis(trimethylsilyl)acetylene from its titanocene complex [{η5-C5Me4(SiMe3)}2Ti(η2-Me3SiC⋮CSiMe3)] (1) afforded the stable titanocene [{η5-C5Me4(SiMe3)}2TiII] (2) in high yield under mild conditions. Compound 2 exhibits paramagnetic line broadening of 1H NMR signals, although it is silent in EPR spectra down to −196 °C. The solid-state structure determination revealed an exactly parallel arrangement of the cyclopentadienyl rings in 2 due to crystallographically imposed symmetry. Complex 2 smoothly reacts with ethylene to give the yellow η2-ethylene complex [{η5-C5Me4(SiMe3)}2Ti(η2-CH2CH2)] (3). The structures of 1 and 3, determined by single-crystal X-ray diffraction, show the bent-titanocene moieties with the η2-coordinated Me3SiC⋮CSiMe3 and CH2CH2 ligands, respectively.

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“…ROP initiators have also been extensively studied in academia and are often based on a Lewis acidic metal, feature one or more alkoxide initiating groups, and are supported by a polydentate ancillary ligand (set), which influences the catalyst nuclearity and controls the coordination−insertion chain growth mechanism. Research into ROP initiators has been extensively reviewed recently. − Many metals have been studied in this context, in particular magnesium, − zinc, ,,− calcium, ,,, aluminum, ,− yttrium, − the lanthanides, − tin, the group 4 elements, ,− germanium, indium, and iron. , …”

Section: Introductionmentioning

confidence: 99%

Ligand Variations in New Sulfonamide-Supported Group 4 Ring-Opening Polymerization Catalysts

et al. 2010

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The synthesis, structures, and ring-opening polymerization (ROP) capability of a wide range of sulfonamide-supported group 4 amide, alkyl, and alkoxide complexes, varying in sulfonamide N-substituent, metal, coordination number, and geometry, are reported. Reaction of Ti(NMe 2 ) 4 or Ti(NMe 2 ) 2 (O i Pr) 2 with MeOCH 2 CH 2 N(CH 2 CH 2 NHSO 2 Me) 2 (12, H 2 N 2 Ms N OMe ) or PhCH 2 N-(CH 2 CH 2 NHSO 2 R) 2 (R = Tol (10, H 2 N 2 Ts N Ph ) or Me (11, H 2 N 2 Ms N Ph )) afforded Ti(N 2 Ms N OMe )-(NMe 2 ) 2 (18), Ti(N 2 Ts 23), and Ti(N 2 Ts N Ph )(O i Pr)(NMe 2 ) (24). Reaction of N(CH 2 CH 2 NHSO 2 R) 3 (R = Tol (13, H 3 N 3 Ts N), Me (14, H 3 N 3 Ms N), or Ar F (15, H 3 N 3 ArF N, Ar F = 3,5-C 6 H 3 (CF 3 ) 2 )) with Zr(CH 2 SiMe 3 ) 4 formed Zr(N 3 R N)(CH 2 SiMe 3 ) (R = Ts (30), Ms (31), or Ar F (32)). Reaction of 15 with Zr(NMe 2 ) 4 gave Zr(N 3ArF N)(NMe 2 ) (33). Complexes 19, 21, 24, 30, 32, and 33 were crystallographically characterized. Monomeric six-or five-coordinate structures were found for the titanium complexes 19, 21, and 24, whereas the zirconium alkyls 30 and 32 were dimeric in the solid state with terminal and bridging κ 2 (N,O)-bound sulfonamides. Complexes 18-24 and 30-33, the previously reported Ti(CyN 2 R )(O i Pr) 2 (25 or 26; CyN 2 R =1,2-C 6 H 10 (NSO 2 Tol) 2 or 1,2-C 6 H 10 -(NSO 2 Mes) 2 ), and in situ generated isopropoxide initiators derived from 30-32 were investigated for the ROP of ε-caprolactone (ε-CL). The four-coordinate 25 was the most active, forming poly(ε-CL) with a relatively narrow PDI and well-controlled M n . Compounds 22, 23, 25, and 26 and isopropoxides generated in situ from 30-32 were all active for the ROP of rac-lactide. Of these, the initiators based on Zr(N 3 R N)(CH 2 SiMe 3 ) (30-32) with i PrOH co-initiator gave good activities and excellent PDIs (1. 08-1.11) and agreement between measured and predicted M n .

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Reactions of ε-Caprolactone with (Alkyne)zirconocene Complexes: Investigation of Elemental Steps in Catalytic Ring-Opening Polymerization of Lactones

Cited by 30 publications

References 34 publications

Bimetallic Titanocene or Zirconocene/Aluminium Complexes as Active Catalysts in Lactone Polymerization Reactions

Bimetallic Titanocene or Zirconocene/Aluminium Complexes as Active Catalysts in Lactone Polymerization Reactions

Bis[η⁵-tetramethyl(trimethylsilyl)cyclopentadienyl]titanium(II) and Its π-Complexes with Bis(trimethylsilyl)acetylene and Ethylene

Ligand Variations in New Sulfonamide-Supported Group 4 Ring-Opening Polymerization Catalysts

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Reactions of ε-Caprolactone with (Alkyne)zirconocene Complexes: Investigation of Elemental Steps in Catalytic Ring-Opening Polymerization of Lactones

Cited by 30 publications

References 34 publications

Bimetallic Titanocene or Zirconocene/Aluminium Complexes as Active Catalysts in Lactone Polymerization Reactions

Bimetallic Titanocene or Zirconocene/Aluminium Complexes as Active Catalysts in Lactone Polymerization Reactions

Bis[η5-tetramethyl(trimethylsilyl)cyclopentadienyl]titanium(II) and Its π-Complexes with Bis(trimethylsilyl)acetylene and Ethylene

Ligand Variations in New Sulfonamide-Supported Group 4 Ring-Opening Polymerization Catalysts

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Bis[η⁵-tetramethyl(trimethylsilyl)cyclopentadienyl]titanium(II) and Its π-Complexes with Bis(trimethylsilyl)acetylene and Ethylene