Bottom-up synthesis of functionalized {Ce4(SiW9O34)2(l)2} polyoxometalates†
Abstract
The reaction of Na10[SiW9O34] with the 4f tetravalent cerium cation associated with four different organic O/N-donor ligands at pH = 4–4.5 gives rise to the formation of five anionic polyoxometalates [Ce4(μ3-O)2(SiW9O34)2(C4H5O4)2]10− (1), [Ce4(μ3-O)2(SiW9O34)2(C5H7O4)2]10− (2), [Ce4(μ3-O)2(SiW9O34)2(C5H8O2–NH3)2]8− (3), [Ce4(μ3-O)2(SiW9O34)2(C6H10O2–NH3)2]8− (4) and [(Ce3(μ3-O)(μ2-OH)3)(Ce6(μ3-O)4(μ3-OH)4)(SiW9O34)4]21− (5). Compounds 1–4 consist of one tetranuclear Ce-based cluster fragment stabilized by two [SiW9O34]10− polyanions and two organic linkers. Compound 5 is composed of a hexanuclear core combined with a trinuclear cerium core, stabilized by four [SiW9O34]10− moieties. The molecular species were characterized by single-crystal and powder X-ray diffraction, IR spectroscopy, TGA, SEM/EDX, SAXS and ICP analysis. The solution stability of compounds 1–4 was also assessed by 29Si and 183W NMR.