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

A series of heterometallic 3d-4f clusters, formulated as Na[Ln(HO)Ni(HO)(SbO)(SbWO)(NiWO)(WO)(CHCOO)]·(HO) [abbreviated as LnNi, where Ln = La (1), Pr (2), and Nd (3)], KNa[Ln(HO)Ni(HO)(SbWO)(WO)(CO)]·(HO) [abbreviated as LnNi, where Ln = La (4), Pr (5), and Nd (6)], and KNa[LnNi(μ-OH)(SbWO)(PWO)(CHCOO)]·(HO) [abbreviated as LnNi, where Ln = Dy (7) and Er (8)], were obtained through the reaction of the lacunary {SbWO} precursor with Ln(NO)·6HO and NiCl·6HO 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 {SbWO} and one Anderson-type {NiWO} building blocks encapsulating one {SbO} cluster, three WO units, three Ln metal ions, and two Ni metal ions. Compounds 4-6 displayed cyclic trimeric aggregates of three {SbWO} units enveloping one CO-templated trinuclear [Ln(CO)] and one WO-templated [Ni(WO)] unit. Compounds 7 and 8 exhibited unique pentameric architectures that featured three 3d-4f cubane clusters of {LnNi(μ-OH)} capped by two {SbWO} and three {PWO} 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.