Bimetallic Reactivity. One-site Addition Two-metal Oxidation Reactions Using a Di-Co(II) Complex of a Binucleating Ligand with 5- and 6-Coordinate Sites

The preparation of an unsymmetrical binucleating ligand bearing a bridging oxadiazole ring flanked on one side
by three ligands and on the other by four ligands is described. When bound to two metals, the ligand forms
complexes where the metals are in 5- and 6-coordinate sites after the incorporation of an exogenous bridging
ligand. A di-Co2+ complex of this ligand has been prepared containing a hydroxide bridge. The complex is readily
oxidized to the di-Co3+ state by outer sphere electron transfer with ferrocenium ions. Addition of Br2 or NO2+
to the di-Co2+ complex leads to the rapid formation of the di-Co3+ bromo or nitro complexes, respectively. The
ligand characteristics which allow for double oxidation with ferrocenium ions and for the one-site addition two-metal oxidations with Br2 and NO2+ are discussed in terms of mechanical coupling between the two metal sites.