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Indenylidene Complexes of Ruthenium Bearing NHC Ligands - Structure Elucidation and Performance as Catalysts for Olefin Metathesis

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Abstract
Second-generation catalysts of the general formula Cl2Ru-(SIMes)(L)(3-phenylinden-1-ytidene), 3a (L = PCy3), 3b (L = PPh3), 3c (L = py), and Cl2Ru(SIMe)(L)(3-phenyhnden-1-yl-idene), 4a (L = PCy3), 4b (L = PPh3), 4c (L = py) were found to be of interest in various metathesis transformations. The catalysts containing SIMe ligands showed improved initiation compared to the more robust SIMes substituted catalysts. A strong temperature effect was noted on all of the reactions tested. Interestingly, complex 3a, showing the lowest initiation rate at room temperature, emerged as the most productive of all systems examined at elevated temperature. It is shown that complexes containing the SIMe ligand display higher initiation efficiency than their corresponding SIMes analogues. Since the higher initiation is related to the ease of phosphane dissociation while phosphane dissociation also promotes catalyst decomposition, complexes bearing the SIMe ligand decompose faster. The complete H-1, C-13 and P-31 resonance assignment and the procedure applied to obtain these from a combination of 1D and 2D NMR techniques, is also reported. Combined with the ROESY technique, these enabled to investigate several conformational processes involving rotations around N-phenyl and C-Ru bonds on the millisecond to second timescale. A clear correlation is demonstrated between the bulkiness of the axial ligand (L) and the rotational freedom of the SIMe(s) ligand. A qualitative analysis also suggests that the extra para-methyl of SIMes leads to additional steric interactions with the 3-phenylinden-1-ylidene ligand. The data reported in this paper demonstrates that substitution patterns of the N-aryl have a significant influence on the activity of the second-generation indenylidene catalysts for a given metathesis reaction.
Keywords
Homogeneous catalysis, PHOSPHINE, EFFICIENT, N-HETEROCYCLIC CARBENE, 4-POLYBUTADIENE SYSTEM, Conformation analysis, CROSS-METATHESIS, Olefin metathesis, Ruthenium, RUCL2(=CHR)(PR(3))(2), Indenylidene, RING-CLOSING METATHESIS, DONOR, ACTIVATION

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Chicago
Monsaert, Stijn, Els De Canck, Renata Drozdzak, Pascal Van Der Voort, Francis Verpoort, José Martins, and Pieter Hendrickx. 2009. “Indenylidene Complexes of Ruthenium Bearing NHC Ligands - Structure Elucidation and Performance as Catalysts for Olefin Metathesis.” European Journal of Organic Chemistry (5): 655–665.
APA
Monsaert, S., De Canck, E., Drozdzak, R., Van Der Voort, P., Verpoort, F., Martins, J., & Hendrickx, P. (2009). Indenylidene Complexes of Ruthenium Bearing NHC Ligands - Structure Elucidation and Performance as Catalysts for Olefin Metathesis. European Journal of Organic Chemistry, (5), 655–665.
Vancouver
1.
Monsaert S, De Canck E, Drozdzak R, Van Der Voort P, Verpoort F, Martins J, et al. Indenylidene Complexes of Ruthenium Bearing NHC Ligands - Structure Elucidation and Performance as Catalysts for Olefin Metathesis. European Journal of Organic Chemistry. 2009;(5):655–65.
MLA
Monsaert, Stijn, Els De Canck, Renata Drozdzak, et al. “Indenylidene Complexes of Ruthenium Bearing NHC Ligands - Structure Elucidation and Performance as Catalysts for Olefin Metathesis.” European Journal of Organic Chemistry 5 (2009): 655–665. Print.
@article{516201,
  abstract     = {Second-generation catalysts of the general formula Cl2Ru-(SIMes)(L)(3-phenylinden-1-ytidene), 3a (L = PCy3), 3b (L = PPh3), 3c (L = py), and Cl2Ru(SIMe)(L)(3-phenyhnden-1-yl-idene), 4a (L = PCy3), 4b (L = PPh3), 4c (L = py) were found to be of interest in various metathesis transformations. The catalysts containing SIMe ligands showed improved initiation compared to the more robust SIMes substituted catalysts. A strong temperature effect was noted on all of the reactions tested. Interestingly, complex 3a, showing the lowest initiation rate at room temperature, emerged as the most productive of all systems examined at elevated temperature. It is shown that complexes containing the SIMe ligand display higher initiation efficiency than their corresponding SIMes analogues. Since the higher initiation is related to the ease of phosphane dissociation while phosphane dissociation also promotes catalyst decomposition, complexes bearing the SIMe ligand decompose faster. The complete H-1, C-13 and P-31 resonance assignment and the procedure applied to obtain these from a combination of 1D and 2D NMR techniques, is also reported. Combined with the ROESY technique, these enabled to investigate several conformational processes involving rotations around N-phenyl and C-Ru bonds on the millisecond to second timescale. A clear correlation is demonstrated between the bulkiness of the axial ligand (L) and the rotational freedom of the SIMe(s) ligand. A qualitative analysis also suggests that the extra para-methyl of SIMes leads to additional steric interactions with the 3-phenylinden-1-ylidene ligand. The data reported in this paper demonstrates that substitution patterns of the N-aryl have a significant influence on the activity of the second-generation indenylidene catalysts for a given metathesis reaction.},
  author       = {Monsaert, Stijn and De Canck, Els and Drozdzak, Renata and Van Der Voort, Pascal and Verpoort, Francis and Martins, José and Hendrickx, Pieter},
  issn         = {1434-193X},
  journal      = {European Journal of Organic Chemistry},
  keywords     = {Homogeneous catalysis,PHOSPHINE,EFFICIENT,N-HETEROCYCLIC CARBENE,4-POLYBUTADIENE SYSTEM,Conformation analysis,CROSS-METATHESIS,Olefin metathesis,Ruthenium,RUCL2(=CHR)(PR(3))(2),Indenylidene,RING-CLOSING METATHESIS,DONOR,ACTIVATION},
  language     = {eng},
  number       = {5},
  pages        = {655--665},
  title        = {Indenylidene Complexes of Ruthenium Bearing NHC Ligands - Structure Elucidation and Performance as Catalysts for Olefin Metathesis},
  url          = {http://dx.doi.org/10.1002/ejoc.200800973},
  year         = {2009},
}

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