Classical/Non-classical Polyoxometalate Hybrids

Abstract

Two polyanions [Se^{I V}₂ Pd^II₄ W^VI₁₄ O₅₆ H]^11- and [Se^{I V}₄ Pd^II₄ W^VI₂₈ O₁₀₈ H₁₂ ]^12- are the first hybrid polyoxometalates in which classical (Group 5/6 metal based) and non-classical (late transition-metal based) polyoxometalate units are joined. Requiring no supporting groups, this co-condensation of polyoxotungstate and isopolyoxopalladate constituents also provides a logical link between POM-Pd^II coordination complexes and the young subclass of polyoxopalladates. Solid-state, solution, and gas-phase studies suggest interesting specific reactivities for these hybrids and point to several potential derivatives and functionalization strategies.

Keywords: 77Se NMR; ESI mass spectrometry; palladium; polyoxometalates; tungsten.

Figure 1

Structure of 1 (a) and the {(H₂O)₃Na}‐1 associate (b); comparison with the {Pd₄O₄(RXO₃)₄} fragment (c) in the cuboid‐shaped polyoxopalladate [MPd₁₂O₈(RXO₃)₈]^z− (d). WO₆ lime green, PdO₄ blue polyhedra; Pd blue, Se/X yellow, O red, Na purple, M light blue. The R groups in {MPd₁₂} are omitted for clarity.

Figure 2

The structure of a {γ‐Pd₂Se₂W₁₃} monomer (a) and a γ‐Pd₂Se₂W₁₃{O=W(H₂O)}₂ moiety (b) in the polyanion 2 (c). WO₆ lime green octahedra, PdO₄ blue squares; Pd blue, Se yellow, O red spheres. The monoprotonated O atoms in the structure of 2 are highlighted in light purple, while aquo ligands are shown in pink.

Figure 3

Room‐temperature ⁷⁷Se NMR spectrum of CsNa‐1 dissolved in 0.25 m LiOAc solution in H₂O/D₂O (pH 6.2).

Figure 4

ESI mass spectrum of 1 in H₂O/acetone (80:20 vol %) solution in negative‐ion mode. Inset: comparison of the calculated and experimentally observed isotope envelopes for the most intense signal (III).