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

Abstract

A novel high-nuclear Ni-substituted poly-( p o l y o x o m e t a l a t e ) [ p o l y ( 1), has been successfully developed and structurally characterized. The polyoxoanion of 1 can be viewed as a unique huge sandwich structure made of an unprecedented Cs 7 (H 2 O) 6 ({Cs 7 }) cluster core encapsulated by two trimeric [(PO 4 )@(Ni 4 (OH) 3 (WO 4 )) 3 @(Bα-PW 9 O 34 ) 3 ] 21− subunits, in which the {Cs 7 } cluster presents an interesting Anderson-like arrangement and is the first example of a classical POM configuration based on the alkali metal cluster in the POM chemistry. The polyoxoanion can also be described as an unusual [(Cs 7 (H 2 O) 6 )@{(PO 4 )@(Ni 4 (OH) 3 (WO 4 )) 3 } 2 ] 19+ cluster packaged by six {PW 9 } fragments. Furthermore, investigations on the Knoevenagel condensation reaction reveal that 1 has good catalytic activity for the condensation of various aldehydes and malononitrile into corresponding products with excellent yields.

Three Double-Layered {Ni8}@{Bn}2 (n = 3, 4, 6) Cluster Sandwiched Polyoxometalates

“…The Knoevenagel condensation of aldehydes with active methylene compounds is one of the most fundamental and widely employed methods for the CC bond construction with a wide range of applications in the synthesis of fine chemicals as well as organic compounds of biomedical significance. − Herein, we studied the catalytic activity of 2 in catalyzing the Knoevenagel condensation at room temperature in methanol solvent. Initially, benzaldehyde and malononitrile were selected as model substrates to conduct the Knoevenagel condensation and a good yield of 88% could be afforded after 30 min; in contrast, the yield was 26% in the absence of catalyst, which indicated that the catalyst played a significant role in the Knoevenagel condensation reaction (Figures S8 and S9).…”

General Strategy for Preparing Uniform Polyoxometalate Microcrystals with Selectively Exposed Low-Index Facets

“…The Knoevenagel condensation reaction, which is an important reaction for the preparation of CC intermediate organic products, was studied to verify the potential heterogeneous catalytic applications. − Benzaldehyde and malononitrile were used as reactants to form benzylidene malononitrile in the representative reaction (Figure a, see details in the Supporting Information). The yield of benzylidene malononitrile for NH 4 –PMo-p is only 75.2% in 120 min at 40 °C (Figure b).…”

Uranyl Polyoxotungstate Cluster for Visible-Light-Driven Heterogeneous C–H Selective Fluorination

“…Six UO 2 2+ groups are connected by six PO 3 OH 2– units to form a wheel-shaped inner core [Na@(UO 2 ) 6 (PO 3 OH) 6 ] + around a Na + ion (Figure a). The conventional sandwich dimeric structure of uranyl–polyoxometalate usually involves two UO 2 2+ cations due to steric considerations. , The introduction of PO 4 3– can coordinate with multiple UO 2 2+ to stabilize the skeleton structure due to its numerous coordination sites and minimal spatial steric hindrance. , As shown in powder X-ray diffraction (Figure S1), the perfect match between the experimental and theoretical values shows that the obtained crystals have high purity and crystallinity. X-ray photoelectron spectroscopy of U 6 P 6 shows peaks with binding energies of 393.0 and 382.1 eV, which can be attributed to the 4f 5/2 and 4f 7/2 electrons of U VI ions (Figure S2).…”

“…to stabilize the skeleton structure due to its numerous coordination sites and minimal spatial steric hindrance. 32,33 As shown in powder X-ray diffraction (Figure S1), the perfect match between the experimental and theoretical values shows that the obtained crystals have high purity and crystallinity. Xray photoelectron spectroscopy of U 6 P 6 shows peaks with binding energies of 393.0 and 382.1 eV, which can be attributed to the 4f 5/2 and 4f 7/2 electrons of U VI ions (Figure S2).…”