OXIDIZED RUTHENIUM FERROCENYLACETYLIDE COMPLEXES, [(ETA-C5H5)L2RUCCFC]PF6 AND [(ETA-C5ME5)L2RUCCFC]PF6 (L = PHOSPHINES) - ELECTRON-DELOCALIZED HETEROBINUCLEAR MIXED-VALENCE COMPLEXES

The reaction of ferrocenylacetylene with (eta-C5R5)L2RuCl [R = H or Me; L2 = 2PPh3, Ph2PCH2CH2PPh2 (dppe), or (Ph2PC5H4)2Fe (dppf)] in the presence of NH4PF6 and the subsequent treatment with alkali gave ruthenium(II) ferrocenylacetylide complexes (eta-C5R5)L2RuCCFc in good yields. Cyclic voltammetric data suggest the large electron delocalization between the Fe atom of the ferrocene moiety and the Ru(II) atom in their one-electron-oxidized complexes. The IR spectra of the oxidized ferrocenylacetylide complexes and the molecular structure of [(eta-C5H5)(Ph3P)2Ru(CCFc)]PF6 determined by X-ray diffraction gave an evidence for such electron delocalization. Crystallographic data for 12 are as follows: space group P2(1)/a, a = 17.176(9) angstrom, b = 12.055(7) angstrom, c = 22.480(9) angstrom, beta = 101.35(4)-degrees, V = 4563(4), Z = 4. The complexes showed low-energy absorption bands assigned to intervalence transfer transitions in the near-infrared (NIR) region. The parameter alpha2, which shows the degree of ground-state delocalization in a mixed-valence complex, is almost as large as that in the [0.0] ferrocenophane monocation. The NIR spectrum, along with the Mossbauer spectra, suggest that the oxidized acetylide complexes are a well electron-delocalized class II type of a heterobinuclear mixed-valence complex.