3D Coordination Polymer of [HW 7 O 24 ] 5– Stabilized by a Copper(II) Complex and Sodium Cations: Structure, Solid‐State Stability, and Aqueous Solution Behavior

Compound Na[Cu(en) 2 ] 2 [HW 7 O 24 ] · 5H 2 O ( 1 , en = ethanediamine), as the first example of a heptatungstate polymer, has been synthesized in H 2 O/dmso and characterized by single‐crystal X‐ray diffraction, IR, UV/Vis, and ESI‐MS. The [HW 7 O 24 ] 5– cluster in 1 , as an inorganic hexadentate ligand, coordinates to two Na + and four [Cu(en) 2 ] 2+ cations to construct a 3D extended structure. The solid‐state stability of 1 at room temperature was proven by X‐ray powder diffraction and digital camera techniques. The electrospray mass spectra suggest that most of the [HW 7 O 24 ] 5– dissociates into relatively more stable [W 6 O 19 ] 2– species in aqueous solution because the coordination bonds around the [HW 7 O 24 ] 5– anions are broken by the solvation effect of water on the the copper cation. These results demonstrate that a transition‐metal‐complex cation plays an important role in the isolation and stabilization of a highly charged polyoxometalate anion.