Electroreduction-Driven Formation and Connectivity of Polyoxometalate Coordination Networks

We present the synthesis of metal oxide coordination networks based on Preyssler-type polyoxoanions ([NaP₅W₃₀O₁₁₀]^14- and [NaP₅MoW₂₉O₁₁₀]^14-) bridged with metal-aquo complexes ([M(H₂O)], M = Co²⁺, Ni²⁺, Zn²⁺, Y³⁺), induced by electrochemical reduction. Networks bridged with first-row transition metals are isostructural with a previously reported Co-bridged structure, while the Y³⁺-bridged structure is new. All networks feature an uncommon binding motif of the metal cation to the oxygen atoms at cap positions, which we hypothesize is due to increased electron density at the cap upon reduction. Oxidation of a Zn²⁺-bridged network resulted in a new structure in which Zn²⁺-O_cap bonds are lost, indicating the importance of reduction in the connectivity of these polyoxometalate-based coordination networks.