Defect {(WVIO7)WVI 4} and Full {(WVIO7)WVI 5} Pentagonal Units as Synthons for the Generation of Nanosized Main Group V Heteropolyoxotungstates

• Published in: Inorganic chemistry 2021-06, Vol.60 (12), p.8917-8923
• Main Authors: Tanuhadi, Elias, Gumerova, Nadiia I, Prado-Roller, Alexander, Mautner, Andreas, Rompel, Annette
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.1c00810

We report on the synthesis and characterization of three new nanosized main group V heteropolyoxotungstates K x Na y [H2​(XWVI 9O33)​(WVI 5O12)​(X2WVI 29O103)]·nH2O {X 3 W 43 } (x = 11, y = 16, and n = 115.5 for X = SbIII; x = 20, y = 7, and n = 68 for X = BiIII) and K8Na15​[H16​(CoII​(H2O)2)0.9​(CoII(H2O)3)2​(WVI 3.1O14)​(SbIIIWVI 9O33)​(SbIII 2WVI 30O106)​(H2O)]·53H2O {Co 3 Sb 3 W 42 }. On the basis of the key parameters for the one-pot synthesis strategy of {Bi 3 W 43 }, a rational step-by-step approach was developed using the known Krebs-type polyoxotungstate (POT) K12[SbV 2WVI 22O74(OH)2]·27H2O {Sb 2 W 22 } as a nonlacunary precursor leading to the synthesis and characterization of {Sb 3 W 43 } and {Co 3 Sb 3 W 42 }. Solid-state characterization of the three new representatives {Bi 3 W 43 }, {Sb 3 W 43 }, and {Co 3 Sb 3 W 42 } by single-crystal and powder X-ray diffraction (XRD), IR spectroscopy, thermogravimetric analysis (TGA), energy-dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), and elemental analysis, along with characterization in solution by UV/vis spectroscopy shows that {Bi 3 W 43 }, {Sb 3 W 43 }, and {Co 3 Sb 3 W 42 } represent the first main group V heteropolyoxotungstates encapsulating a defect {(WVIO7)­WVI 4} ({X 3 W 43 }, X = BiIII and SbIII) or full {(WVIO7)­WVI 5} ({Co 3 Sb 3 W 42 }) pentagonal unit. With 43 tungsten metal centers, {X 3 W 43 } (X = BiIII and SbIII) are the largest unsubstituted tungstoantimonate– and bismuthate clusters reported to date. By using time-dependent UV/vis spectroscopy, the isostructural representatives {Sb 3 W 43 } and {Bi 3 W 43 } were subjected to a comprehensive study on their catalytic properties as homogeneous electron-transfer catalysts for the reduction of K3[FeIII(CN)6] as a model substrate revealing up to 5.8 times higher substrate conversions in the first 240 min (35% for {Sb 3 W 43 }, 29% for {Bi 3 W 43 }) as compared to the uncatalyzed reaction (