Solvothermal synthesis and selected properties of {[Ni(dien)₂]₃[V₆As₈O₂₆]}²⁺·2 Cl– featuring the small [V₆ IVAs₈ IIIO₂₆]⁴– cluster anion

A new arsenato-polyoxovanadate with the composition {[Ni(dien) 2 ] 3 [V 6 As 8 O 26 ]} 2+ ·2 Cl – has been crystallized under solvothermal conditions as turquoise block-like crystals. The central structural feature is the [V 6 IV As 8 III O 26 ] 4– cluster anion, which is composed of two trinuclear {V 3 O 11 } groups consisting of three edge-sharing VO 5 polyhedra. Pairs of pyramidal AsO 3 moieties share a common corner forming As 2 O 5 units, which interconnect the {V 3 O 11 } groups. One of the [Ni(dien) 2 ] 2+ complexes adopts the s-fac (Ni1) and the second complex the mer configuration (Ni2). The Cl − anion is involved in strong hydrogen bonding interactions and links the [Ni(dien) 2 ] 2+ complexes to form twelve-membered rings which host the [V 6 As 8 O 26 ] 4– cluster anions. The Hirshfeld surface analysis yields a detailed picture of the intermolecular interactions revealing clear differences for the two unique [Ni(dien) 2 ] 2+ complexes. Intermolecular contacts also include As⋯H, O⋯H and H⋯H interactions. In the electronic spectrum the bands of d – d transitions of the vanadyl group and of the Ni 2+ cations overlap, preventing a detailed analysis.