Anion-Dependent Assembly of Heterometallic 3d–4f Clusters Based on a Lacunary Polyoxometalate

A series of heterometallic 3d-4f clusters, formulated as Na₁₇[Ln₃(H₂O)₅Ni^II(H₂O)₃(Sb₄O₄)(SbW₉O₃₃)₃(Ni^IIW₆O₂₄)(WO₂)₃(CH₃COO)]·(H₂O)₆₅ [abbreviated as Ln₃Ni₂, where Ln = La³⁺ (1), Pr³⁺ (2), and Nd³⁺ (3)], K₅Na₁₁[Ln₃(H₂O)₃Ni^II₃(H₂O)₆(SbW₉O₃₃)₃(WO₄)(CO₃)]·(H₂O)₄₀ [abbreviated as Ln₃Ni₃, where Ln = La³⁺ (4), Pr³⁺ (5), and Nd³⁺ (6)], and K₃Na₂₇[Ln₃Ni^II₉(μ₃-OH)₉(SbW₉O₃₃)₂(PW₉O₃₄)₃(CH₃COO)₃]·(H₂O)₈₀ [abbreviated as Ln₃Ni₉, where Ln = Dy³⁺ (7) and Er³⁺ (8)], were obtained through the reaction of the lacunary {SbW₉O₃₃} precursor with Ln(NO₃)₃·6H₂O and NiCl₂·6H₂O in a NaAc/HAc buffer in the presence of different anions. Single-crystal X-ray structure analysis revealed that compounds 1-3 possessed tetrameric architectures featuring three Keggin-type {SbW₉O₃₃} and one Anderson-type {Ni^IIW₆O₂₄} building blocks encapsulating one {Sb₄O₄} cluster, three WO₂ units, three Ln³⁺ metal ions, and two Ni²⁺ metal ions. Compounds 4-6 displayed cyclic trimeric aggregates of three {SbW₉O₃₃} units enveloping one CO₃^2--templated trinuclear [Ln₃(CO₃)]⁷⁺ and one WO₄^2--templated [Ni^II₃(WO₄)]⁺ unit. Compounds 7 and 8 exhibited unique pentameric architectures that featured three 3d-4f cubane clusters of {LnNi₃(μ₃-OH)₃} capped by two {SbW₉O₃₃} and three {PW₉O₃₄} building blocks. Interestingly, the structural regulation of the heterometallic 3d-4f clusters in the polyoxometalate systems with trimers, tetramers, and pentamers was realized by introducing different anions.