Novel ruthenium allenylidene and mixed alkynyl allenylidene complexes:: Crystal structure of trans-[(Ph2PCH2CH2PPh2)2Ru(CCPh)(=C=C=CPh2)]PF6

cis-RuCl2(dppe)(2) (1) (dppe = Ph2PCH2CH2PPh2) reacts with propargylic alcohols, HC=(CCRROH)-R-1-O-2, and NaPF6 to give a variety of allenylidene complexes trans-[(dppe)(2)(Cl)Ru+=C=C=(CRR2)-R-1]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)(2)Ru(C=CR)(=C=C=(CRR2)-R-1)]PF6 (7, 8). These derivatives have been fully characterized by IR, H-1, C-13, and P-31 NMR. Single-crystal X-ray diffraction is determined for 7c (R = R-1 = R-2 = 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.