A {Co4O4} Cubane Incorporated within a Polyoxoniobate Cluster

Abstract A novel octacobalt‐containing polyoxoniobate, Na 6 K 12 [H 2 Co 8 O 4 (Nb 6 O 19 ) 4 ]⋅39 H 2 O, has been prepared by a combination of hydrothermal and diffusion methods. The polyanion [H 2 Co 8 O 4 (Nb 6 O 19 ) 4 ] 18− incorporates a tetrameric assembly of Lindqvist‐type [Nb 6 O 19 ] 8− fragments trapping a {Co II 4 Co III 4 } cluster which comprises a central {Co III 4 O 4 } cubane core, surrounded by another four Co II ions linkers. Furthermore, magnetic measurements show that the compound exhibits antiferromagnetic interactions.