A μ-AsO₄-Bridging Hexadecanuclear Ni-Substituted Polyoxotungstate

Abstract

A novel tetrahedral μ-AsO 4 -bridging hexadecanuclear Ni-substituted silicotungstate (ST) Na 21 H 10 [(AsO 4 )-{Ni 8 (OH) 6 (H 2 O) 2 (CO 3 ) 2 (A-α-SiW 9 O 34 ) 2 } 2 ]•60H 2 O (1) was made by the reactions of trivacant [A-α-SiW 9 O 34 ] 10− ({SiW 9 }) units with Ni 2+ cations and Na 3 AsO 4 •12H 2 O and characterized by IR spectrometry, elemental analysis, thermogravimetric analysis (TGA), and powder X-ray diffraction (PXRD). 1 contains a novel polyoxoanion [(AsO 4 ){Ni 8 (OH) 6 (H 2 O) 2 (CO 3 ) 2 (A-α-SiW 9 O 34 ) 2 } 2 ] 31− built by four trivacant Keggin [A-α-SiW 9 O 34 ] 10− fragments linked through an unprecedented [(AsO 4 )-{Ni 8 (OH) 6 9+ cluster, where the tetrahedral AsO 4 acts as an exclusively μ 2 -bridging unit to link multiple Ni centers; such a connection mode appears for the first time in polyoxometalate chemistry. Furthermore, the electrochemical and catalytic oxidation properties of compound 1 have been investigated.

Three Lanthanide-Functionalized Antimonotungstate Clusters with a {Sb4O4Ln3(H2O)8} Core: Syntheses, Structures, and Properties

“…Although the mechanism involved in the process of catalytic oxidation is ambiguous, we speculate that the oxidant H 2 O 2 first interacts with catalyst 1 to form the peroxo POM active species, which subsequently transfers the active oxygen atoms to the substrates of sulfides and returns to the initial 1 to restart the catalytic cycle (Figure S13). , The catalytic activity of 1 is higher than many reported POM-based catalysts (Table S4), which may be related to the existence of more active oxygen atoms (protonated oxygen) in the structure of 1a , which is consistent with the literature. , …”

“…70,71 The catalytic activity of 1 is higher than many reported POM-based catalysts (Table S4), which may be related to the existence of more active oxygen atoms (protonated oxygen) in the structure of 1a, which is consistent with the literature. 72,73 Moreover, it is not hard to see that 2 has good reusability from Figure 6; the catalytic activity hardly weakens after five cycling tests (>97% conversion and 100% selectivity). IR spectra and PXRD patterns before and after the reaction confirm the stability of 2 in the catalytic process (Figure S14).…”

Two Ni-Substituted Trilacunary Keggin-Type Polyoxometalates: Syntheses, Crystal Structures, NLO Studies, and Magnetic Properties

“…For the past few years, transition-metal-substituted polyoxotungstates (TMSPs) have aroused much concern in polyoxometalate (POM) chemistry owing to their intriguing architectural diversity and potential applications in electrochemistry, magnetism, catalysis, nonlinear optics, etc. − Up to now, many TMSPs with attractive structures have been designed and synthesized. Among them, lacunary POMs were considered to be an excellent precursor in the synthesis of TMSPs because of abundant terminal oxygen atoms, which endows them with excellent nucleophilic ability to capture excessive metal ions. − These lacunary polyanions are extremely active to various transition-metal (TM) ions and can be regarded as multidentate O-donor ligands to attract the construction of high-nuclear TM clusters, thus producing a variety of TMSPs with interesting physical and chemical properties. − Among various TMSPs, the nickel-containing TMSPs are extremely interesting and have been widely explored as a result of their fascinating structural diversity, such as monomer, dimer, , trimer, tetramer, hexamer, octamer, , etc. For instance, Yang’s group has obtained a series of TMSPs hybrids with structures from isolated clusters to 3-D frameworks by using Ni-substituted POMs as structural building units and organic ligands as stabilizers or linkers under hydrothermal conditions, which greatly enriches the family of POMs. − …”

“…5−7 These lacunary polyanions are extremely active to various transition-metal (TM) ions and can be regarded as multidentate O-donor ligands to attract the construction of high-nuclear TM clusters, thus producing a variety of TMSPs with interesting physical and chemical properties. 8−10 Among various TMSPs, the nickel-containing TMSPs are extremely interesting and have been widely explored as a result of their fascinating structural diversity, such as monomer, 11 dimer, 12,13 trimer, 14 tetramer, 15 hexamer, 14 octamer, 16,17 etc. For instance, Yang's group has obtained a series of TMSPs hybrids with structures from isolated clusters to 3-D frameworks by using Ni-substituted POMs as structural building units and organic ligands as stabilizers or linkers under hydrothermal conditions, which greatly enriches the family of POMs.…”

{Ti6}/{Ti10} Wheel Cluster Substituted Silicotungstate Aggregates

“…Polyoxometalates (POMs), as types of classic metal–oxygen clusters, have a history of nearly 200 years and present diversiform architectures of different sizes and shapes. − The design and synthesis of novel POM materials have always been very valuable works due to their extensive potential applications in various fields such as photophysics, electrochemistry, magnetism, catalysis, medicine, and so on. − In the enormous family of POMs, the synthetic chemistry of transition-metal-substituted POMs (TMSPs) has experienced rapid development and generally has become the leading subject of POM science. − So far, a feasible strategy for making new TMSPs is using lacunary POM fragments as the structure-directing agents (SDAs) to induce the TM cations into the lacunary sites of POMs. − During the process of assembly, under the influence of experimental conditions such as pH and temperature, the lacunary fragments undergo a configuration transformation to form one or more types of building units that can cooperate each other to induce TM cation aggregation, resulting in the emergence of novel TMSP species with structural diversity and unique physicochemical properties. − …”