RELATIONSHIPS BETWEEN STRUCTURE AND REDOX PROPERTIES OF RU4(CO)12(MU-4-ETA-2-C2PH2) AND [ET4N]2[RU4(CO)11(MU-4-ETA-2-C2PH2)]

The cyclic voltammograms of Ru4(CO)12(C2Ph2) (1) contain three irreversible peaks. The initial two-electron reduction of 1 is followed by loss of a CO ligand, and the product was identified spectroscopically in a bulk electrochemical experiment. This product, [Et4N]2[Ru4(CO)11(C2Ph2)] (3), was also prepared independently by chemical reduction of 1 with Na/Hg. On the basis of variable scan rate experiments and the digital simulation of these cyclic voltammograms, the overall electrochemistry can be described by a mechanism involving at least six species. Of the six species, two (compounds 1 and 3) have been isolated and structurally characterized. The electrochemistry of 3 was elucidated by variable scan rate experiments and digital simulation. A single-crystal X-ray structure determination of 3 reveals a dinegative anion containing a butterfly Ru4 core, a mu-4-eta-2-C2Ph2 and two bridging and nine terminal CO ligands. Crystal data: monoclinic, a = 12.135 (1) angstrom, b = 18.078 (2) angstrom, C = 20.583 (2) angstrom, beta = 104.79 (1)degrees, P2(l)/n, Z = 4, final R(F) = 0.031, R(w)(F) = 0.036.