Bridged binuclear bis(dithiolene) complexes of iron and cobalt

Abstract

Magnetic moments of the binuclear complexes are consistent with those of analogous mononuclear five-coordinate adducts reported earlier. Cobalt complexes with R = CFd, z = 0, 2 - , and L-L = 1,4-bis(diphenylphosphino)benzene, bis(dipheny1phosphino)acetylene (DPPA), or trans-1,2-bis(diphenylphosphino)ethy~ene (DPFE) were studied in the most detail Polarography in dichloromethane reveals a three-member electron-transfer series (z = 2 -, 1 -, 0). Half-wave potentials for the two redox processes of the bridged complexes and the 1 - 0 process of the mononuclear triphenylphosphine analog occur in a range of only 0.2 V, indicating that in the former the cobalt-dithiolpne units behave as essentially independent sites in electron-transfer reactions. Mononuclear adducts of L-L formed in the presence of excess bridging ligand were detected by polarography and epr. Solutions containing equimolar amounts of dianionic complexes with L = DPPA and DPPE were found to exhibit electronic absorption bands at 6850 and respectively, which are attributed to intramolecular electron The bridging ligands contain nitrogen or phosphorus donor atoms.