Issue 24, 2021

Deeply reduced empty Keggin clusters [Mo IVxM VI12−xO40−xpyx] (x = 3, 6; M = Mo, W; py = pyridine): synthesis, structures, and Lewis field catalysis

Abstract

In this research, we present the first examples of MoIV3–WVI hybrid polyoxometalates (MoIV3-POMs) with empty Keggin structures: α-[MoIV3MoVIWVI8O31(OH)6py3]·2Hpy·4H2O (1·2Hpy·4H2O), γ-[MoIV6WVI6O28(OH)6py6]·2[H2N(CH3)2]·6.5H2O (2·2[H2N(CH3)2]·6.5H2O), γ-[MoIV6WVI6O29(OH)5py6Na(H2O)5]·2[NH2(CH3)2]·2H2O (3·2[NH2(CH3)2]·2H2O) and γ-[{MoIV6MoVIWVI5O28(OH)6py6}2Znpy4]·2Hpy·8H2O (4·2Hpy·8H2O). They were prepared through the solvothermal partial oxidation of a mixture of triangular bioxo-capped hexacarboxylate clusters [MoIVxWIV3−xO2(O2CCH3)6L3]q (x = 0–3, L = H2O, q = 2+; L = CH3CO2, q = −1), providing a feasible route to the designed synthesis of mixed MoIV3–W POMs. The much lower yield and poor repeatability of 1 compared to those of 2, 3, and 4 are ascribed to the fact that the triangularly MoIV–MoIV bonded MoIV3 Lewis acid cluster unit of the former results from the breakage of MIV–WIV bonds (M = Mo, W) and recombination of MoIV in the Na[MoIVWIV2O2(O2CCH3)9] precursor because of the extremely easy oxidation of WIV to WVI as compared to MoIV. 2, 3, and 4 exhibit highly LCF-dependent (LCF = Lewis catalysis field) hydrogen transfer catalysis performance in the hydrazine reduction of nitrobenzene to aniline.

Graphical abstract: Deeply reduced empty Keggin clusters [MoIVxMVI12−xO40−xpyx] (x = 3, 6; M = Mo, W; py = pyridine): synthesis, structures, and Lewis field catalysis

Supplementary files

Article information

Article type
Research Article
Submitted
24 Aug 2021
Accepted
11 Okt 2021
First published
11 Okt 2021

Inorg. Chem. Front., 2021,8, 5178-5185

Deeply reduced empty Keggin clusters [MoIVxMVI12−xO40−xpyx] (x = 3, 6; M = Mo, W; py = pyridine): synthesis, structures, and Lewis field catalysis

C. Ren, Z. Lu, B. Luo, X. Yi, L. Lin and L. Xu, Inorg. Chem. Front., 2021, 8, 5178 DOI: 10.1039/D1QI01080H

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