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Volumn 28, Issue 2, 2009, Pages 606-620

Group 4 metal complexes of fhiorous (Di)alkoxide-(Di)imino ligands: synthesis, structure, olefin polymerization catalysis, and decomposition pathways

Author keywords

[No Author keywords available]

Indexed keywords

CATALYSIS; CHELATION; ETHYLENE; HAFNIUM; HYDROGEN; LIGANDS; METAL COMPLEXES; MONOMERS; PARAFFINS; POLYMERIZATION; POLYMERS; TITANIUM COMPOUNDS; ZIRCONIUM;

EID: 61949154873     PISSN: 02767333     EISSN: None     Source Type: Journal    
DOI: 10.1021/om8009409     Document Type: Article
Times cited : (33)

References (121)
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    • For reviews and leading articles on post-metallocene complexes of groups 3-5 and the lanthanides related to polymerization, see
    • For reviews and leading articles on "post-metallocene" complexes of groups 3-5 and the lanthanides related to polymerization, see:
  • 20
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    • For selected examples of early transition metal complexes bearing fluorous alkoxide ligands
    • For selected examples of early transition metal complexes bearing fluorous alkoxide ligands:
  • 31
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    • 2OH; see:
    • 2OH; see:
  • 34
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    • Jacobsen, E. N. Catalytic Asymmetric Synthesis; Ojimal., Ed.; VCH: Weinheim, 1993; p 159.
    • (a) Jacobsen, E. N. Catalytic Asymmetric Synthesis; Ojimal., Ed.; VCH: Weinheim, 1993; p 159.
  • 35
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    • Wilkinson, G, Stone, F. G. A, Abel, E. W, Hegedus, L. S, Eds, Pergamon Press: New York, Chapter 11.1
    • (b) Jacobsen, E. N. Comprehensive Organometallic Chemistry II; Wilkinson, G.; Stone, F. G. A.; Abel, E. W.; Hegedus, L. S., Eds.; Pergamon Press: New York, 1995; Vol. 12,Chapter 11.1.
    • (1995) Comprehensive Organometallic Chemistry II , vol.12
    • Jacobsen, E.N.1
  • 59
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    • Benzyl complexes of zirconium and hafnium proved also to be sensitive when exposed to light, as solutions in hydrocarbons
    • Benzyl complexes of zirconium and hafnium proved also to be sensitive when exposed to light, as solutions in hydrocarbons.
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    • Gilli, G.; Cruickshank, D. W. J.; Beddoes, R. L.; Mills, O. S. Acta Crystallogr., B Struct. Crystallogr. Cryst. Chem. 1972, 28, 1889.
    • (b) Gilli, G.; Cruickshank, D. W. J.; Beddoes, R. L.; Mills, O. S. Acta Crystallogr., B Struct. Crystallogr. Cryst. Chem. 1972, 28, 1889.
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    • In a C2-symmetric environment such as in structure B (Figure 1, D, or E (Figure 3, two doublets are expected for the diastereotopic hydrogens of the CHH ligand unit adjacent, as well as for the diastereotopic hydrogens of CHHPh groups in dibenzyl complexes 7 and 8. Also, the 'F NMR spectrum would feature two quartets for the nonequivalent C (CF3, CF 3) groups; see refs 4a,b
    • 3) groups; see refs 4a,b.
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    • 4
    • R1,R2)H led to intractable mixtures of compounds. We assume that the latter difficulties reflect the versatile redox chemistry of Ti, combined with the identified decomposition pathways of dibenzyl-metal (Zr, Hf) complexes of these new ligands. It is noteworthy that, to our knowledge, there is no dibenzyl-titanium complex of "regular" phenoxyimine ligands reported thus far; see refs 8 and 9.
  • 77
    • 61949262122 scopus 로고    scopus 로고
    • 2, as the main isolable product (see Experimental Section).
    • 2, as the main isolable product (see Experimental Section).
  • 78
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    • For selected examples of decomposition pathways of early transition metal complexes involving hydrogen abstraction, see
    • For selected examples of decomposition pathways of early transition metal complexes involving hydrogen abstraction, see:
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    • 2, via proton abstraction from the OH and CUH groups; see Experimental Section.
    • 2, via proton abstraction from the OH and CUH groups; see Experimental Section.
  • 88
    • 61949373864 scopus 로고    scopus 로고
    • To prevent this decomposition pathway, the use of gem-dimethyl- substituted pro-ligand analogues was attempted. Surprisingly, fluorous (di)imino, di)ols such as HOC (CF3)2CMe2C (iPr)=N (iPr) and [HOC, CF3)2CMe2C (iPr)=NCH2-]2 were found not to react with M (CH 2Ph)4 (M, Ti, Zr, Hf) in toluene up to 60-80 °C, temperatures at which the latter precursors start decomposing at a significant rate. Reasons for this absence of reactivity, while no obvious steric and electronic effects can be accounted for, remain obscure. To date, such gem-dimethyl-substituted pro-ligands could be installed only at aluminum centers, under conditions much more drastic than those used for the parent nonsubstituted pro-ligands; see ref 11
    • 4 (M = Ti, Zr, Hf) in toluene up to 60-80 °C, temperatures at which the latter precursors start decomposing at a significant rate. Reasons for this absence of reactivity, while no obvious steric and electronic effects can be accounted for, remain obscure. To date, such gem-dimethyl-substituted pro-ligands could be installed only at aluminum centers, under conditions much more drastic than those used for the parent nonsubstituted pro-ligands; see ref 11.
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    • The reactions of Zr (CH2Ph)4 with 1 equiv of {ONMc,Ph)H or {ONph,ph}H were attempted to potentially access the corresponding Zr (CH2Ph)2{ON-R1,R2} complexes. However, in both cases, NMR monitoring showed that these reactions led to ca. 1:1 mixtures of Zr (CH2Ph)4 and Zr (CH 2Ph)2{ONR1,R2}2, which further evolve by decomposition of the latter species into Zr (CH2Ph){ON- R1,R2){ONR1,R2, Those observations indicate that disproportionation of the putative intermediate species [Zr (CH 2Ph)3, ONR1,R2, or consecutive reaction of the latter species with {ONph,ph}H (to form in both cases Zr (CH 2Ph)2{ONR1,R2}2) is faster than abstraction of a hydrogen atom from the ligand backbone
    • 2) is faster than abstraction of a hydrogen atom from the ligand backbone.
  • 103
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    • Complexes 1 and 2 were also briefly investigated in polymerization catalysis, although no valuable performance was expected, considering the equatorial coordination of the tetradentate ligand and the anticipated absence of cis vacant sites in the resulting cationic species. As a matter of fact, for instance, when complex 1 was activated with MAO (1000 equiv, toluene solution), no polymerization activity was observed (1 atm ethylene, 25 °C).
    • Complexes 1 and 2 were also briefly investigated in polymerization catalysis, although no valuable performance was expected, considering the equatorial coordination of the tetradentate ligand and the anticipated absence of cis vacant sites in the resulting cationic species. As a matter of fact, for instance, when complex 1 was activated with MAO (1000 equiv, toluene solution), no polymerization activity was observed (1 atm ethylene, 25 °C).
  • 109
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    • In these experiments, polyethylene was recovered in virtually the same amount as that of ethylene consumed; oligomers (if any) were therefore negligible
    • In these experiments, polyethylene was recovered in virtually the same amount as that of ethylene consumed; oligomers (if any) were therefore negligible.
  • 110
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    • w = 143-452,000, Mw/Mn = 3.4-5.7; see:
    • w = 143-452,000, Mw/Mn = 3.4-5.7; see:
  • 112
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    • Zr (CH2Ph)2{PyC (CF3) 2O}2/MAO (1:1000) gave at 30 °C, 8 atm, 10 kg PE mol-1 h-1 with Mw, 375 000, M wMn, 28; Zr (CH2Ph)2{PyC (CF3)2O}2/B (C6F5)3 (1:1) gave at 40 °C, 3 atm, 96 kg PE mol-1 h-1 with Mw, 16 000, Mw/Mn, 2.6; see ref 3d
    • n = 2.6; see ref 3d.
  • 113
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    • Berg and Kress observed insignificant or no ethylene polymerization activity with Zr (CH2Ph) 2[RN{CH2CH 2C (O)R'2h]/B (C6Fs) 3 and Zr (CH2PhM2,6- bis{menthoxo)pyridyl)/B (C6F5) 3 combinations, respectively, and attributed it to the formation of tight ion pairs; see ref 34a and: Gauvin, R. M; Osborn, J. A, Kress, J. Organometallics 2000, 19, 2944
    • 3 combinations, respectively, and attributed it to the formation of tight ion pairs; see ref 34a and: Gauvin, R. M; Osborn, J. A.; Kress, J. Organometallics 2000, 19, 2944.
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    • 2]/ MAO combination exhibits modest ethylene polymerization activity (20 °C, 1 atm); see: Mack, H.; Eisen, M. J. Chem. Soc., Dalton Trans. 1998, 917.
    • 2]/ MAO combination exhibits modest ethylene polymerization activity (20 °C, 1 atm); see: Mack, H.; Eisen, M. J. Chem. Soc., Dalton Trans. 1998, 917.
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    • 3 has been removed).
    • 3 has been removed).
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* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.