Multicomponent Cooperative Assembly of Nanoscale Boron-Rich Polyoxotungstates with 22 and 30 Boron Atoms

Abstract

This work demonstrates that the introduction of positive lanthanide (Ln) and transition metal (TM) cations into polyoxotungstates (POTs) to stabilize negative oxoboron clusters is a feasible and general synthetic strategy for creating not only rare boron-rich POTs but also intriguing multicomponent composite polyoxometalates (POMs). By this strategy, a large family of unprecedented boron-rich POTs with 22 and 30 boron atoms, such as [(B 18 Si 3 Ln 6 O 36 (OH) 14 ){B 4 Ni 4 O 10 (OH) 4 (A-α-SiW 9 O 34 )} 3 ] 44− (1Ln), [(B 19 Si 2 Ln 7 O 35 (OH) 15 (H 2 O)){B 4 Ni 4 O 10 (OH) 4 (A-α-SiW 9 O 34 )} 2 {B 3 Ni 4 O 9 (OH) 3 (A-α-SiW 9 -O 34 )}] 41− (2Ln), where Ln is Gd, Tb, and Dy, and [(B 22 O 42 ) {LnNi 3 (OH) 3 (B-α-SiW 9 O 34 )} 4 ] 34− (3Ln; Ln is Sm, Gd, and Tb), have been obtained. These POTs incorporate the largest number of boron atoms and the highest-nuclearity oxoboron clusters of any molecular POTs reported to date. The results show the fusion of two distinct research areas of POT chemistry and oxoboron cluster chemistry. In addition, they also show a family of unique POMs made from multiple oxo clusters including W-O, B-O, TM-O, and Ln-O. Experiments indicate these novel composite materials can exhibit effective catalytic activity for oxidizing toxic 2-chloroethyl ethyl sulfide.

Hepta-Zr-Incorporated Polyoxometalate Assembly

“…Polyoxometalates (POMs), as well-defined anionic oxo-metal clusters, have been extensively studied for almost two centuries due to their abundant structural diversity and excellent properties suitable for catalysis, magnetism, optical materials, and biological medicine. − In the large POM community, considerable progress has been made in the design and assembly of transition-metal-substituted POMs. − Since the first Zr-substituted POM (ZrSP) [Zr 3 (μ 2 -OH) 3 (A-β-SiW 9 O 34 ) 2 ] 11– was obtained, ZrSPs have aroused intensive motivation and enthusiasm on account of their aesthetic characteristics and catalytic performance. − However, compared with other transition metal Mn/Fe/Co/Ni/Cu-substituted POMs, the easy hydrolyzation of Zr ions limits the development of ZrSPs (Table S1). Hence, developing novel high-nuclear ZrSPs with excellent performance in catalysis remains a challenge in POM chemistry.…”

Chiral {Ni6PW9} Cluster–Organic Framework: Synthesis, Structure, and Properties

“…Polyoxometalates (POMs) have attracted increasing attention due to their various applications in medication, magnetism, and catalysis. − However, trilacunary POMs as precursors can induce the aggregation of transition metal (TM) cations to form TM–oxo clusters under hydrothermal conditions, producing a class of TM-substituted POMs (TMSPs) with interesting physicochemical properties, − which make it the potential structure building units (SBUs) to build POM cluster–organic frameworks (POMCOFs). − However, POMCOFs are still difficult to make because of the following considerations: (1) organic amines are easy to chelate on the TM cations as bidentate ligands rather than bridging ligands. (2) POMs are polyanionic clusters that preferentially bind to TM cations rather than rigid ligands like carboxylate anions.…”

High-Nuclear Ni-Substituted Poly(polyoxometalate) Containing an Anderson-like {Cs7} Cluster

“…Knoevenagel condensation that utilizes the dehydration coupling reaction of a carbonyl group and an active methylene compound is one of the most common and important organic reaction for the construction of the CC bond, which has been widely employed in many important fields, such as pharmaceutical intermediates, calcium antagonists, fine chemicals, polymers, etc. − Thus, it is a very meaningful work to develop efficient, stable, and recyclable catalysts to accelerate the Knoevenagel condensation reaction under mild reaction conditions. POMs have received extensive attention in the field of catalysis due to their good thermal and oxidative stability compared to organocatalysts and organometallic catalysts, , and there have been some reports of POMs that show excellent catalytic activities in the Knoevenagel condensation reaction. − Herein, the catalytic performance of 1 as a heterogeneous catalyst for the Knoevenagel condensation reaction of aldehydes and malononitrile in methanol solvent was studied (Scheme ). The product yields of the reactions were detected by gas chromatography with flame ionization detection using dodecane as an internal standard and calculated based on the aldehydes (Figure S7).…”