SYNTHESIS, STRUCTURE AND REDOX CHEMISTRY OF 1,2-BIS(RUTHENOCENYL)-ETHYLENE DERIVATIVES - A NOVEL STRUCTURAL REARRANGEMENT TO A (MU-ETA(6)ETA(6)-PENTAFULVADIENE)DIRUTHENIUM COMPLEX UPON 2-ELECTRON OXIDATION

Formylruthenocene, 1-formyl-1',2',3',4',5'-pentamethylruthenocene and 1-formyl-2,3,4,5-tetramethylruthenocene were treated with TiCl4-Zn in thf to afford the corresponding ethylene derivatives trans-1,2-bis(rut henocenyl)ethylene, is(1',2',3',4',5'-pentamethylruthenocenyl)ethylene and s-1,2-bis(2,3,4,5-tetramethylruthenocenyl)ethylene in excellent y ields. Similarly, the dimethyl analogs were obtained from acetylruthen ocene and 1-acetyl-1',2',3',4',5'-pentamethylruthenocene in good yield s. Cyclic voltammograms of the ethylene complexes showed an irreversib le two-electron oxidation wave at significantly lower potential than t hat of pentamethylruthenocene or ruthenocene. Two-electron chemical ox idation of these complexes with p-benzoquinone-BF3. OEt2 gave stable d icationic (mu-eta(6): eta(6)-pentafulvadiene)diruthenium complexes in moderate yields. The molecular structures of five complexes were deter mined by X-ray diffraction.