title: Rapid Markovnikov addition of HCl to a pendant alkyne: evidence for a quinoidal cumulene.
abstract: Reaction of cis-[RuCl2(dppm)2]BF4 with TlBF4 and 1,4-diethynyl-benzenes results in the formation of the vinylidene cations trans-[Ru([double bond, length as m-dash]C[double bond, length as m-dash]CH-C6H2-2,5-R2-4-C[triple bond, length as m-dash]CH)Cl(dppm)2](+) (R = H, Me). Subsequent reaction with [N(n)Bu4]Cl results in nucleophilic attack at the coordinated organic ligand, but not at the expected metal-bound carbon atom. Instead, trans-[Ru(C[triple bond, length as m-dash]C-C6H2-2,5-R2-4-CCl[double bond, length as m-dash]CH2)Cl(dppm)2] was generated which, when coupled with DFT calculations, provides evidence for an intermediate quinoidal cumulene complex.
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham DH1 3LE, UK.
authors.forename: Samantha G
authors.initials: SG
authors.lastname: Eaves
authors.forename: Sam J
authors.initials: SJ
authors.lastname: Hart
authors.forename: Adrian C
authors.initials: AC
authors.lastname: Whitwood
authors.forename: Dmitry S
authors.initials: DS
authors.lastname: Yufit
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Low
authors.forename: Jason M
authors.initials: JM
authors.lastname: Lynam