Double Trigonal Pyramidal {SeO ₃ } Groups Bridging Gadolinium-Substituted Dawson Selenotungstate for Catalytic Synthesis of Isoindolinones

A novel double trigonal pyramidal {SeO₃}-bridged, gadolinium-substituted Dawson-type selenotungstate, (NH₄)₈Na₁₀[GdSeW₂O₈(H₂O)₅]₂[Se₂W₁₄O₅₂]₂·41H₂O (GdSeW), was successfully synthesized through a one-step assembly strategy. The most striking feature of its structure lies in the dual role of {SeO₃}, not only functioning as a heteroatom template to construct Dawson-type {Se₂W₁₄O₅₂} units, but also acting as a linker to bridge the two units, thereby forming a dumbbell-shaped architecture. Furthermore, GdSeW exhibits remarkable catalytic activity as a Lewis acid catalyst for the condensation reaction of 2-acetylbenzoic acid and amines, affording the valuable isoindolinones with yields up to 96%. The catalytic system demonstrates broad substrate compatibility, efficiently accommodating a range of benzylamines, anilines, and aliphatic amines. Control experiments and recycling tests confirm the heterogeneous nature and stability of GdSeW under reaction conditions. This work expands the structural diversity of lanthanide-containing polyoxometalates and highlights their potential application in organic transformations.