Polyoxometalate-Dicarboxylate Hybrid Dimers with {SiW₁₀Cr₂} Nodes: Syntheses, Structures, and Mass Spectrometric Characterization

The current study describes a new family of hybrid dimers constructed from secondary building blocks based on a dichromium-substituted silicodecatungstate, {SiW₁₀Cr₂}, and flexible dicarboxylate ligands of varied lengths. All five polyoxometalate-organic hybrid compounds exhibit an entropically favored, cyclic dimer motif that contains just two {SiW₁₀Cr₂} clusters─the minimum to form a closed loop, linked by two aliphatic dicarboxylates, as revealed by single-crystal X-ray diffraction. Due to the kinetic inertness of such Cr³⁺-based hybrid dimers, ESI-MS has become a particularly useful technique for the characterization of these paramagnetic, NMR-unfriendly systems.