Platinum-containing isopolytungstates: [Pt ₃ W ₁₁ O ₄₁ ] ^6.4− with a linear {Pt ₃ O ₁₂ } triad, [Pt ^II ₂ W ₅ O ₁₈ ((CH ₃ ) <sub>2

The platinum-containing isopolytungstates [Pt₃W₁₁O₄₁]^6.4− (<strong>Pt₃W₁₁</strong>), [Pt^II₂W₅O₁₈((CH₃)₂AsO₂)₂]⁴⁻ (<strong>Pt^II₂W₅</strong>), and [Pt^III₂W₅O₁₈((CH₃)₂AsO₂)₄]⁴⁻ (<strong>Pt^III₂W₅</strong>) have been synthesized in aqueous media and characterized by single-crystal XRD and multinuclear (¹⁹⁵Pt, ¹³C, ¹H) NMR spectroscopy. The polyanion [Pt₃W₁₁O₄₁]^6.4− comprises three {W₃O₁₃} and one {W₂O₁₀} fragments connected by three platinum atoms forming a linear {Pt₃O₁₂} triad exhibiting direct Pt–Pt bonding (2.64 to 2.68 Å). The distances between the two outer Pt ions and oxygens from neighboring <strong>Pt₃W₁₁</strong>clusters (2.34 and 2.65 Å, respectively) are consistent with [4+1] coordination. Quantum mechanical calculations allowed assigning the Pt oxidation states for the mixed-valence polyanion <strong>Pt₃W₁₁</strong>. The polyanion <strong>Pt^II₂W₅</strong> comprises a monolacunary {W₅O₁₈}⁶⁻ Lindqvist fragment coordinated by two Pt^II ions with square-planar coordination and two terminal dimethylarsinate groups, exhibiting a ¹⁹⁵Pt NMR signal at 610 ppm in water. On the other hand, <strong>Pt^III₂W₅</strong> comprises two Pt^III ions with square-pyramidal coordination and direct Pt–Pt bonding (2.64 Å). The polyanions <strong>Pt₃W₁₁</strong> and <strong>Pt^II₂W₅</strong> were immobilized on SBA-15-apts and then tested as precatalysts for the hydrogenation of o-xylene under continuous-flow, high pressure hydrogenation conditions.