Decavanadate‐based Transition Metal Hybrids as Bifunctional Catalysts for Sulfide Oxidation and C—C Bond Construction

Abstract

Main observation and conclusion The development of bifunctional catalysts has drawn much attention in realizing efficient and feasible catalytic systems to meet the diverse demand of potential industrial applications. Design of stable and powerful bifunctional catalysts for various catalysis systems is highly desirable yet largely unmet. Here, three kinds of decavanadate‐based transition metal hybrids (DTMH) (i.e., Co‐DTMH, Ni‐DTMH and Ag‐DTMH) have been successfully synthesized through a pH tuning strategy and further characterized. Specifically, the rare MO5N six‐coordinated transition metal coordination modes have been detected in Co‐DTMH and Ni‐DTMH, while Ag atoms in Ag‐DTMH exhibited three‐ and five‐coordinated geometries with the tuning of specially selected imidazole ligands. Thus‐obtained clusters can serve as powerful bifunctional catalysts for both sulfide oxidation and C—C bond construction. Remarkably, Ag‐DTMH demonstrated excellent heterogeneous bifunctional catalytic properties in the selective oxidation of sulfides and construction of C—C bond (yields up to 99%), which enable successful recycling for three cycles with remained catalytic activities and structure stability. The newly designed decavanadate‐based transition metal hybrids with bifunctional property hold high promise in the practical applications like continuous catalysis or flow bed reactions.

Polyoxometalate‐based Inorganic‐Organic Hybrids as Heterogeneous Catalysts for Asymmetric and Tandem Reactions

“…[57] For instance, transition metal-decorated imidazole derivatives stabilized decavanadate clusters and resulted in the formation of bifunctional catalysts. Among them, [44] The combination of transition metal ions with POM polyoxoanions or heteropoly acids can endow them with both Lewis acid-base or Lewis-Brønsted acidic sites. Tian and coworkers reported the synthesis of [Zn(bix)]{V 2 O 6 } (bix = 1,4bis(imidazole-1-ylmethyl)benzene) as a bifunctional Lewis acidbase catalyst for CÀ C bond formation through Knoevenagel and cyanosilylation reaction in solvent-free conditions.…”

“…For example, in the presence of Co(OAc) 2 and isopropyl imidazole (1‐ip‐IM), single crystals of [Co(1‐ip‐IM)(H 2 O) 5 ] 2 (H 2 V 10 O 28 ).6H 2 O were isolated while replacing Co(OAc) 2 with AgNO 3 resulted in a powder product. Hence, 1‐Et‐IM was used to react with AgNO 3 and afforded the single crystals of [Ag(1‐Et‐IM) 2 ] 2 [Ag 2 (1‐Et‐IM) 4 ] 2 [H 3 V 10 O 28 ] 2 .2(1‐Et‐IM).2H 2 O [44] …”

In situ ball-milling gram-scale preparation of polyoxoniobate-intercalated MgAl-layered double hydroxides for selective aldol and Michael addition cascade reactions

“…Polyoxometalates (POMs) are a class of negatively charged metal oxide clusters with tailorable crystalline structures, which consist of high-valence early transition metals and have great potential for applications in the fields of electrochemistry, 1 catalysis, 2 sensing detection, 3 photochemistry, 4 energy chemistry, 5 etc . Nevertheless, the facile dissolution and difficulty of separating the POMs in a homogeneous system to increase the accessible space for the catalytic reaction are fatal drawbacks in various POM-catalysed organic reactions, such as esterification, 6 olefin epoxidation, 7 alcohol oxidation, 8 etc .…”

Self-Assembly of a U(VI)-Containing Polytungstate Tetramer with Lewis Acid-Base Catalytic Activity for a Dehydration Condensation Reaction

“…Pyrazoles are important compounds in the fields of pharmaceutical chemistry, agricultural chemistry, and synthetic organic chemistry. − The direct condensation of hydrazines with 1,3-diketones is a more efficient method to successfully obtain pyrazole derivatives; it represents the most straightforward and effective method owing to significantly high overall reaction efficiencies and improved atom economy . Traditionally, Lewis acids or Brønsted acids are applied as catalysts for this transformation, such as Sc­(OTf) 3 , sulfuric acid, and so on. − Recently, it was reported that the Lewis acid-base catalytic system would be beneficial for this reaction. ,− However, there are very rare examples of the condensation reaction of hydrazines with 1,3-diketones catalyzed by the bifunctional Lewis acid-base catalyst up to now. − The development of efficient bifunctional catalysts for the construction of pyrazoles still is a significant work in current research.…”