N-Heterocyclic carbene-induced transmethylation in tungsten imido alkylidene bistriflates: unexpected formation of an N-heterocyclic olefin complex.

The reaction of [W(N-2,6-PrCH)(CHCMePh)(OTf)(DME)] (DME = 1,2-dimethoxyethane, OTf = CFSO) with the N-heterocyclic carbene (NHC) 1,3-bis(2,4,6-trimethylphenyl)imidazolidin-2-ylidene (IMesH) leads to DME activation followed by transmethylation and in due consequence to the formation of the N-heterocyclic olefin complex [W(N-2,6-PrCH)(CHCMePh)(OTf)(IMesHCH)] along with [W(N-2,6-PrCH)(CHCMePh)(OTf)(IMesH)(κ-O(CH)OMe)], [1,3-bis(2,4,6-trimethylphenyl)-2-methylimidazolidinium (OTf)] and [1,3-bis(2,4,6-trimethylphenyl)-2-H-imidazolidinium (OTf)]. A reaction pathway is proposed and confirmed by the use of C-labelled compounds; structures of the products were verified by NMR and/or single-crystal X-ray analysis.