Abnormally Bound N-Heterocyclic Carbene Complexes of Ruthenium:C-H Activation of Both C4 and C5 Positions in the Same Ligand

摘要

Ruthenium N-heterocyclic carbene(NHC)complexes have been the focus of considerable interest owing to their applications in a range of homogeneous catalytic processes.'11 However,some of these precatalysts have been shown to undergo degradation reactions under quite mild conditions,suggesting that M-NHC bonds may not be as robust as once believed.121 This is further substantiated by a number of reports detailing Ru-NHC complexes that prove susceptible to intramolecular C-X(X = H,C,N)bond cleavage,migratory insertion,and cyclopropanation/rearrangement.