Synthesis and Characterization of Alkoxide-Bridged Heterometallic Clusters of Cerium and Copper.

We prepared alkoxide-bridged heterometallic clusters of cerium and copper by the complexation of two metal alkoxides: treatment of Ce(OBu) with [Cu(OBu)] in a 1:1 metal ratio produced an alkoxide-bridged tetranuclear cluster, CeCu(OBu) (). Upon adding 4-substituted pyridine derivatives to complex , trinuclear clusters, CeCu(OBu)() (: L = DMAP (4-dimethylaminopyridine); : L = BPY (4,4'-bipyridine)), were obtained along with the release of 0.25 equiv of [Cu(OBu)], in which a three-coordinated copper center was involved. In contrast, reaction of with 4 equiv of 2,6-dimethylphenylisocyanide (XylNC) and 0.5 equiv of [Cu(OBu)] resulted in the selective formation of CeCu(OBu)(CNXyl) (). In addition, CeK(OBu) was used for complexation with CuCl by salt-elimination, giving CeCuCl(OBu) () including a five-coordinated copper center. These complexes - were characterized by crystal structure determination as well as cyclic voltammetry of , , and . The cyclic voltammogram of in CHCl and THF suggested that reorganization of the coordination sphere around the copper center was observed for during the Cu(I/II) redox processes assisted by the coordination of THF.