η1-vinylidene formation from internal alkynones by C-C bond migration

The [mu(2)-N-2{CpRu(PPh3)(2)}(2)](2+) (1(2+)) dication is a source of the formal 16-electron [CpRu(PPh3)(2)](+) fragment, and it reacts with internal alkynes such as 1,3-diphenylpropynone, 4phenyl-3-butyn-2-one, and 3-cyclopropyl-l-phenylpropynone to yield ill-vinylidene complexes 2a(+)-2c(+) by C-C bond activation. In the case of 1,3-diphenylpropynone, the eta(1)-ketone complex [CpRu(PPh3)2[PhC(eta(1)-O)C CPh)]+ (3a(+)) was isolated as its PF6- salt, and it is apparently an intermediate in the formation of the vinylidene complex. Complexes 2a(+)-2c(+) were characterized as their BAr4F- [ArF = 3,5-bis(trifluoromethyl)phenyl] salts by NMR and IR spectroscopic methods, ESI-MS, and EA. The single crystal X-ray diffraction structure of 2aBAr(4)(F) is presented. These reactions represent the first examples where an internal alkyne undergoes C-C bond migration to form an eta(1)-vinylidene complex.