Engineering geometric metamorphosis in {P6M2Mo16O73}-based high-nuclearity metal superclusters: from tetrahedral to square assemblies via topological transformations

The synthesis of superclusters is vital for understanding their self-assembly mechanisms, requiring precise control over composition, orientation, and connectivity. The tenets of reticular chemistry afford a systematic approach to the architectural design and regulation of molecular entities, thereby enabling the fulfillment of preconceived structural objectives. Herein, the strategic introduction of transition metal ions, Co^II and Ni^II, has enabled the controlled formation of two novel closely related anionic superclusters based on the {Sr⊂P₆M₂Mo₁₆O₇₃} clusters: Co₁₂Sr₄Mo₈₀P₃₆ (1) and Na₄Ni₂₃Sr₄Mo₈₈P₅₂ (2). The former manifests a tetrahedral structure, while the latter, derived from topological transformations of cluster 1, exhibits a unique square geometry. Structural elucidation revealed that the integration of Mo^V ions in a reduced state, in concert with distinct transition metal ions (Co^II and Ni^II), plays a pivotal role in determining the geometric profiles of these superclusters. Furthermore, clusters 1 and 2 demonstrate efficacy as heterogeneous catalysts, significantly promoting the transformation of methyl phenyl sulfide (MPS) to methyl phenyl sulfoxide (MPSO).