Synthesis and Characterization of Cerium-Oxo Clusters Capped by Acetylacetonate.

Cerium-oxo clusters have applications in fields ranging from catalysis to electronics and also hold the potential to inform on aspects of actinide chemistry. Toward this end, a cerium-acetylacetonate (acac) monomeric molecule, Ce(acac) (), and two acac-decorated cerium-oxo clusters, [CeO(acac)(CHO)(CHOH)]·10.5MeOH () and [CeO(OH)(acac)(CHCOO)]·6(CHCN) (), were prepared and structurally characterized. The Ce(acac) monomer contains Ce. Crystallographic data and bond valence summation values for the and clusters are consistent with both clusters having a mixture of Ce and Ce cations. Ce L-edge X-ray absorption spectroscopy, performed on , showed contributions from both Ce and Ce. The cluster is built from a hexameric cluster, with six Ce sites, that is capped by two dimeric Ce units. By comparison, , which formed upon dissolution of in acetonitrile, consists of a central decamer built from edge sharing Ce hexameric units, and two monomeric Ce sites that are bound on the outer corners of the inner Ce core. Electrospray ionization mass spectrometry data for solutions prepared by dissolving in acetonitrile showed that the major ions could be attributed to Ce clusters that differed primarily in the number of acac, OH, MeO, and O ligands. Small angle X-ray scattering measurements for dissolved in acetonitrile showed structural units slightly larger than either Ce or Ce in solution, likely due to aggregation. Taken together, these results suggest that the acetylacetonate supported clusters can support diverse solution-phase speciation in organic solutions that could lead to stabilization of higher order cerium containing clusters, such as cluster sizes that are greater than the Ce and Ce reported herein.