Facile migratory insertion of a N-heterocyclic carbene into a ruthenium-carbon double bond: A new type of reaction of a NHC ligand

The reaction of [RuCp(IPri)(CH3CN)2]PF6 (IPri = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with HC=CR (R = COOMe, COOEt, COMe) yields the allyl carbene complexes [RuCp(=C(R)-η3-CHC(R)CH-IPri)]PF6. This conversion involves selective head-to-tail coupling of two alkynes and an unusual migratory insertion of the N-heterocyclic carbene into the ruthenium-carbon double bond of a ruthenacyclopentatriene intermediate. Copyright © 2006 American Chemical Society.