Two Series of Cu II ‐Substituted Sandwich‐Type Polyoxotungstates Constructed from Trivacant Germanotungstate Fragments

Under hydrothermal conditions, two families of new Cu II ‐substituted sandwich‐type germanotungstates (GTs): Cu 6 ‐GTs (enH 2 ) 2 [Cu(en) 2 ] 2 [Cu 6 (en) 2 (H 2 O) 2 (B‐α‐GeW 9 O 34 ) 2 ]⋅4H 2 O ( 1 ), H 4 [Cu(deta)(H 2 O)] 2 [Cu 6 (en) 2 (H 2 O) 2 (B‐GeW 9 O 34 ) 2 ]⋅8H 2 O ( 2 ), [Cu(en)(H 2 O) 2 ] 2 [Cu(en) 2 ] 2 [Cu 6 (en) 2 (H 2 O) 2 (B‐α‐GeW 9 O 34 ) 2 ]⋅8H 2 O ( 3 ) (en=ethylenediamine, deta=diethylenetriamine) and Cu 4 ‐GTs H 4 [Cu(H 2 O) 4 ] 2 [Cu(H 2 O) 5 ] 2 [Cu 4 (H 2 O) 2 (B‐α‐GeW 9 O 34 ) 2 ]⋅8H 2 O ( 4 ), H 10 [Cu(H 2 O) 3 (Cl)] 2 [Cu 4 (B‐α‐GeW 9 O 34 ) 2 ]⋅8H 2 O ( 5 ), H 8 [Na(H 2 O) 4 ] 2 [Cu(H 2 O) 3 (Cl)] 2 [Cu 4 (B‐α‐GeW 9 O 34 ) 2 ]⋅8H 2 O ( 6 ) have been made and characterized. Single‐crystal structural analyses indicate that 1–3 contain a belt‐like hexa‐Cu II substituted sandwich‐type [Cu 6 (en) 2 (H 2 O) 2 (B‐α‐GeW 9 O 34 ) 2 ] 8+ unit. Notably, 1–3 are rare organic‐inorganic hybrid polyoxometalates with [Cu 6 (en) 2 (H 2 O) 2 (B‐α‐GeW 9 O 34 ) 2 ] 8− subunits, displaying the assembly from 1‐D chain to 3‐D framework by the [Cu(en) 2 ] 2+ or [Cu(deta) 2 (H 2 O)] 2+ linkers. 4–6 contain rhomb‐like tetra‐Cu II substituted sandwich‐type [Cu 4 (H 2 O) n (B‐α‐GeW 9 O 34 ) 2 ] 12− (n=2, 0) units linked by [Cu(H 2 O) 4 ] 2+ or [Cu 2 (H 2 O) 6 Cl 2 ] + clusters to from 1‐D chain. Magnetic measurements performed on 3 indicate the occurrence of ferromagnetic interactions within the copper ions. Furthermore, the electrochemical and electro‐catalysis properties of 3 have been studied in 0.02 M H 2 SO 4 + 0.5 M Na 2 SO 4 solution, and show good electro‐catalytic activity to the reduction of nitrite.