Cyclization Accompanied with 1,2-Phenyl Migration in the Protonation of Ruthenium Acetylide Complex Containing an Allenyl Group

Reaction of the ruthenium allenylidene complex [Ru]=C=CPh2 (1 [Ru] = Cp(PPh3)(2)Ru) with the propargylic Grignard reagent R C CCH2MgBr (R = CH3 CH2CH3 Ph) yielded a mixture of two acetylide complexes The major products [Ru]C CCPh2C(R)=C=CH2 (2a R = CH3 2b R = CH2CH3 2c R = Ph) have an allenyne moiety and the minor ones [Ru]C CCPh2CH2C CR (3a R = CH3 3h R = CH2CH3 3c R = Ph) have a diyne ligand The reaction of similar propargyl Grignard reagent HC CCH2MgBr with 1 yielded only the diyne complex 3d Treatment of complexes 2a-2c with HBF4 afforded the cyclization complexes 5a-5c respectively proceeding via a vinylidene intermediate The cyclization of the allenyl and the vinylidene groups is accompanied with a phenyl group migration Complex 5b is fully characterized by a single-crystal X ray diffraction analysis Similar cyclization of complexes 2a and 2b catalyzed by a Au phosphine complex gave the ruthenium vinylidene complexes 6a and 6b respectively with different selectivity from that of the protonation reaction Au catalyzed cyclization of the diyne complex 3d yielded 6d which is fully characterized by a single crystal X ray diffraction analysis