TY - JOUR
T1 - Ru-based olefin metathesis catalysts bearing ph-responsive n-heterocyclic carbene (NHC) ligands
T2 - Activity control via degree of protonation
AU - Balof, Shawna L.
AU - Yu, Bing
AU - Lowe, Andrew B.
AU - Ling, Yan
AU - Zhang, Yong
AU - Schanz, Hans Jörg
PY - 2009/5
Y1 - 2009/5
N2 - Olefin metathesis catalysts (H2ITap)(PCy3)Cl2Ru=CHPh (4)and (H2ITap)Cl2Ru=CH-(C6H4-O-iPr) (5)[H2ITap = 1,3-bis-(2-,6-dimethyl-4- dimethylaminophenyl)-4,5-dihydroimid-azol-2-ylidene] were used for the ring-opening metathesispolymerization (ROMP) of exo-7-oxanorbornene derivative 7in the presence of various amounts of acid. Upon gradualprotonation of the NMe2 groups of the H2Tap ligand, the me-tathesis activity of both catalysts were gradually reduced dueto electronic changes of the N-heterocyclic carbene (NHC)ligand donor capability. The investigation of the ROMP poly-mer 8, DFT calculations and measurements of the initiationkinetics prove that the reduced activity is solely due to re-duced rates of propagation.
AB - Olefin metathesis catalysts (H2ITap)(PCy3)Cl2Ru=CHPh (4)and (H2ITap)Cl2Ru=CH-(C6H4-O-iPr) (5)[H2ITap = 1,3-bis-(2-,6-dimethyl-4- dimethylaminophenyl)-4,5-dihydroimid-azol-2-ylidene] were used for the ring-opening metathesispolymerization (ROMP) of exo-7-oxanorbornene derivative 7in the presence of various amounts of acid. Upon gradualprotonation of the NMe2 groups of the H2Tap ligand, the me-tathesis activity of both catalysts were gradually reduced dueto electronic changes of the N-heterocyclic carbene (NHC)ligand donor capability. The investigation of the ROMP poly-mer 8, DFT calculations and measurements of the initiationkinetics prove that the reduced activity is solely due to re-duced rates of propagation.
KW - Carbene ligands
KW - Densityfunctional calculations
KW - Metathesis
KW - N-Heterocyclic carbenes
KW - Ring-opening polymerization
KW - Ruthenium
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U2 - 10.1002/ejic.200801145
DO - 10.1002/ejic.200801145
M3 - Article
AN - SCOPUS:66149179255
SN - 1434-1948
SP - 1717
EP - 1722
JO - European Journal of Inorganic Chemistry
JF - European Journal of Inorganic Chemistry
IS - 13 SPEC. ISS.
ER -