{Ti₁₂} Cluster-Added Poly(polyoxometalate) Containing Mixed Trivacant Keggin and Dawson Fragments

A new high-nuclear Ti-oxo-cluster-added poly(polyoxometalate) Cs₂Na₁₉H₁₂[(Cs@Ti₁₂O₁₈)@{(A-α-SiW₉O₃₄) (P₂W₁₅O₅₆)₃}]·29H₂O (1) has been made by reacting two types of trivacant precursors with TiOSO₄under hydrothermal conditions. The polyoxoanion of 1 contains one Keggin-type [A-α-SiW₉O₃₄]^10-and three Dawson-type [P₂W₁₅O₅₆]^12-fragments that synergistically induce the Ti⁴⁺ions to aggregate at vacant sites, resulting in a large {Ti₁₂}-oxo-cluster cavity sealing a Cs⁺ion. It is worth noting that the {Ti₁₂} cluster is built by three edge-shared Ti₃O₁₃({Ti₃}¹) cores and one corner-shared Ti₃O₁₅({Ti₃}²) core bridged via 6 μ₂-O, which has never been seen before in polyoxometalate chemistry. Significantly, 1 represents the first example of [A-α-SiW₉O₃₄]^10-and [P₂W₁₅O₅₆]^12-simultaneously participating in making poly(polyoxometalate).