Platinum-containing isopolytungstates: [Pt3W11O41]6.4- with a linear {Pt3O12} triad, [PtII2W5O18((CH3)2AsO2)2]4- and [PtIII2W5O18((CH3)2AsO2)4]4- featuring direct Pt-Pt bonds

Identifier:  imarina:9484698

Handle: https://hdl.handle.net/20.500.11797/imarina9484698

Authors:  Zhang, Jiayao; Bhattacharya, Saurav; Mahmoud, Mahmoud Elcheikh; Nisar, Talha; Merimi, Khaoula; Lopez, Xavier; Poblet, Josep M; Wagner, Veit; Kortz, Ulrich

Abstract:
The platinum-containing isopolytungstates [Pt3W11O41]6.4- (Pt3W11), [PtII2W5O18((CH3)2AsO2)2]4- (PtII2W5), and [PtIII2W5O18((CH3)2AsO2)4]4- (PtIII2W5) 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 & Aring;). The distances between the two outer Pt ions and oxygens from neighboring Pt3W11 clusters (2.34 and 2.65 & Aring;) are consistent with [4+1] coordination. Quantum mechanical calculations enabled the assignment of Pt oxidation states for the mixed-valence polyanion Pt3W11. The polyanion PtII2W5 contains a monolacunary {W5O18}6- Lindqvist fragment coordinated via two PtII ions in square-planar geometry and two terminal dimethylarsinate groups, exhibiting a 195Pt NMR signal at 610 ppm in water. By contrast, PtIII2W5 comprises two PtIII ions with square-pyramidal coordination and direct Pt-Pt bonding (2.64 & Aring;). The polyanions Pt3W11 and PtII2W5 were immobilized on SBA-15-apts and then tested as precatalysts for the hydrogenation of o-xylene under continuous-flow, high-pressure conditions.