Unprecedented Trapping of Difluorooctamolybdate Anions within an α‑Polonium Type Coordination Network

New fluorinated hybrid solids [Mo₂F₂O₅(tr₂pr)] (1), [Co₃(tr₂pr)₂(MoO₄)₂F₂]·7H₂O (2), and [Co₃(H₂O)₂(tr₂pr)₃(Mo₈O₂₆F₂)]·3H₂O (3) (tr₂pr = 1,3-bis­(1,2,4-triazol-4-yl)­propane) were prepared from the reaction systems consisting of Co­(OAc)₂/CoF₂ and MoO₃/(NH₄)₆Mo₇O₂₄, as Co^II and Mo^VI sources, in water (2) or in aqueous HF (1, 3) employing mild hydrothermal conditions. The tr₂pr ligand serves as a conformationally flexible tetradentate donor. In complex 1, the octahedrally coordinated Mo atoms are linked in the discrete corner-sharing {Mo₂(μ₂-O)­F₂O₄N₄} unit in which a pair of tr-heterocycles (tr = 1,2,4-triazole) is arranged in cis-positions opposite to “molybdenyl” oxygen atoms. The anti–anti conformation type of tr₂pr facilitates the tight zigzag chain packing motif. The crystal structure of the mixed-anion complex salt 2 consists of trinuclear [Co₃(μ₃-MoO₄)₂(μ₂-F)₂] units self-assembling in Co^II-undulating chains (Co···Co 3.0709(15) and 3.3596(7) Å), which are cross-linked by tr₂pr in layers. In 3, containing condensed oxyfluoromolybdate species, linear centrosymmetric [Co₃(μ₂-tr)₆]⁶⁺ SBUs are organized at distances of 10.72–12.45 Å in an α-Po-like network using bitopic tr-linkers. The octahedral {N₆} and {N₃O₃} environments of the central and peripheral cobalt atoms, respectively, are filled by triazole N atoms, water molecules, and coordinating [Mo₈O₂₆F₂]^6– anions. Acting as a tetradentate O-donor, each difluorooctamolybdate anion anchors four [Co₃(μ₂-tr)₆]⁶⁺ units through their peripheral Co-sites, which consequently leads to a novel type of a two-nodal 4,10-c net with the Schläfli symbol {3².4³.5}­{3⁴.4²⁰.5¹⁶.6⁵}. The 2D and 3D coordination networks of 2 and 3, respectively, are characterized by significant overall antiferromagnetic exchange interactions (J/k) between the Co^II spin centers on the order of −8 and −4 K. The [Mo₈O₂₆F₂]^6– anion is investigated in detail by quantum chemical calculations.