Expansion of Zirconium Oxide Clusters by 3d/4f Ions

Inorg Chem. 2021 Aug 2;60(15):11599-11608. doi: 10.1021/acs.inorgchem.1c01526. Epub 2021 Jul 21.

Abstract

Two series of charge-neutral coordination clusters featuring quasi-isostructural metal oxide cores, isolated as [Zr6Fe2Ln2O8(ib)14(bda)2(NO3)2xMeCN (Ln = La (1), Ce (2), Pr (3), and Nd (4); ib- = isobutyrate; H2bda = N-butyldiethanolamine) and [Zr6Fe2Ln2O8(ib)14(mda)2(NO3)2xMeCN (Ln = La (5), Ce (6), Pr (7), and Nd (8); H2mda = N-methyldiethanolamine), were obtained via one-pot reactions of [Fe3O(ib)6(H2O)3]NO3 as a critical precursor, Ln(NO3)3·6H2O (Ln = La, Ce, Pr, and Nd), the respective aminoalcohol, and [Zr6O4(OH)4(ib)12(H2O)]·3Hib in an acetonitrile solution. The coordination clusters in 1-8 feature {Zr6O8} cores that are structurally expanded by two 4f (Ln3+) and two 3d (Fe3+) metal ions, each individually coordinated to one of the eight oxide centers of {Zr6O8}, producing a metal skeleton where the 3d/4f positions cap four of the triangular faces of the central Zr6 octahedron. The coordination clusters differ in the chosen aminoalcohol coligands, N-butyldiethanolamine or N-methyldiethanolamine, which lead to a different isobutyrate coordination pattern in the two series, while the {Fe2Ln2Zr6O8} core structure remains virtually unaffected. All eight coordination clusters are obtained in moderate to good yields of 29-66% after only several days. Complexes 1-8 are stable against air and moisture; they are also surprisingly thermally stable up to 280 °C in air and in nitrogen atmosphere, and they represent the first reported examples of 3d/4f-functionalized zirconium oxide clusters.