Abstract
The influence of the structure of cationic molybdenum imido alkylidene N-heterocyclic carbene (NHC) catalysts, i. e. of Mo(N-2-tert-butyl-C6H4) (CHCMe2Ph)(NHC)X+ B(ArF)4 (NHC=1,3-di(2-Pr) imidazol-2-ylidene (iPr), 1,3-dimesitylimidazol-2-ylidene (IMes); X=pyrrolide, OCH(CF3)2, B(ArF)4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) and of Mo(N-3,5-Me2-C6H3)(CHCMe2Ph)(NHC)(CH3CN)X+ B(ArF)4 (NHC=1,3-dimesitylimidazol-2-ylidene, 1,3-dimesitylimidazolin-2-ylidene (IMesH2); X=CF3SO3, OCPh(CF3)2) on E/Z-selectivity in the ring-opening cross-metathesis (ROCM) of endo, endo-2,3- dicarbomethoxynorborn-5-ene (endo, endo-DCMNBE), exo, exo-2,3-dicarbomethoxynorborn-5-ene (exo, exo- DCMNBE), endo, exo-2,3-dicarbomethoxynorborn-5-ene ((+) DCMNBE) and 2,3-exo,exo-bis(acetoxymethyl)- 7-oxabicyclo2.2.lhept-5-ene (7-oxa-NBE) with 1-pentene, styrene, allyltrimethylsilane, allyl benzyl ether, allyl phenyl ether and allyl ethyl ether has been studied. With the exception of the ROCM reaction of endo, endo-DCMNBE with styrene, all other ROCM reactions of endo, endo-DCMNBE proceeded under thermodynamic control without any post-metathesis isomerization reactions with full retention of the configuration of the newly formed 1,2-disubstituted double bond as confirmed by kinetic studies. Similar accounts for selected homometathesis reactions. Catalyst structure-selectivity correlations based on the buried volume, Vbur, of the N-imido ligand are presented. All primary data files and processed data of the journal article from Buchmeiser group.
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