Novel Ruthenium Allenylidene and Mixed Alkynyl Allenylidene Complexes:  Crystal Structure of trans-[(Ph2PCH2CH2PPh2)2Ru(C⋮CPh)(CCCPh2)]PF6

cis-RuCl2(dppe)2 (1) (dppe = Ph2PCH2CH2PPh2) reacts with propargylic alcohols, HC⋮CCR1R2OH, and NaPF6 to give a variety of allenylidene complexes trans-[(dppe)2(Cl)Ru+CCCR1R2]PF6 (6). The subtitution of the chloride from vinylidene trans-[(dppe)2(Cl)RuCCHR] cations, in the presence of a base, by a variety of propargylic alcohols constitutes the easiest way to selectively produce complexes containing both the alkynyl and the allenylidene groups, trans-[(dppe)2Ru(C⋮CR)(CCCR1R2)]PF6 (7, 8). These derivatives have been fully characterized by IR, 1H, 13C, and 31P NMR. Single-crystal X-ray diffraction is determined for 7c (R = R1 = R2 = Ph). Complexes 7 react with strong nucleophiles such as NaOMe or NaBH4 to form exclusively unsymmetrical bis(acetylide) complexes by addition of H- or MeO- on the carbon C(3) of the allenylidene ligand. Cyclic voltammetry of complexes 6 and 7 shows the marked influence of the terminal groups of the allenylidene ligands on the reduction of the ruthenium(II) center.