Heterometallic Clusters with Multiple Rare Earth Metal-Transition Metal Bonding.

Although a series of complexes with rare earth (RE) metal-metal bonds have been reported, complexes which have multiple RE-Rh bonds are unknown. Here we present the identification of the first example of a molecule containing multiple RE-Rh bonds. The complex with multiple Ce-Rh bonds was synthesized by the reduction of a d-f heterometallic molecular cluster Ce{N[(CH2CH2NPiPr2)RhCl(COD)]3} with excess potassium-graphite. The oxidation state of Ce in 3a appears to be a mixture of Ce(III) and Ce(IV), which was confirmed by X-ray photoelectron spectroscopy, magnetism, and theoretical investigations (DFT and CASSCF). For comparison, the analogous species with multiple La(III)-Rh and Nd(III)-Rh bonds were also constructed. This study provides a possible route for the construction of complexes with multiple RE metal-metal bonds and an investigation of their potential properties and applications.