Platinum-containing isopolytungstates: [Pt₃W₁₁O₄₁]^6.4− with a linear {Pt₃O₁₂} triad, [Pt^II₂W₅O₁₈((CH₃)₂AsO₂)₂]⁴⁻ and [Pt^III₂W₅O₁₈((CH₃)₂AsO₂)₄]⁴⁻ featuring direct Pt–Pt bonds

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