Heteropoly Acid-Based Materials for Reversible H₂ Storage as Protons and Electrons under Mild Conditions

Heteropoly Acid-Based Materials for Reversible H2 Storage as Protons and Electrons under Mild Condition

Sandwich-Type Zinc-Containing Polyoxometalates with a Hexaprismane Core [{Zn₂W(O)O₃}₂]⁴⁺ Synthesized by Thermally Induced Isomerization of a Metastable Polyoxometalate

Two novel sandwich-type silicotungstates, TBA8[{Zn2W(O)O3}2H4{α-SiW9O33}2]·5H2O (α-Zn4; TBA = tetra-n-butylammonium) and TBA8[{Zn2W(O)O3}2H4{β-SiW9O33}2]·7H2O (β-Zn4), were synthesized by the solid-state thermally induced isomerization of metastable TBA8[{Zn(OH2)(μ3-OH)}2{Zn(OH2)2}2{γ-HSiW10O36}2]·9H2O (γ-Zn4). Compounds α-Zn4 and β-Zn4 consisted of two [SiW9O33]8− subunits sandwiching the unprecedented distorted hexaprismane core [{Zn2W(O)O3}2]4+

Sandwich-Type Zinc-Containing Polyoxometalates with a Hexaprismane Core [{Zn₂W(O)O₃}₂]⁴⁺ Synthesized by Thermally Induced Isomerization of a Metastable Polyoxometalate

Two novel sandwich-type silicotungstates, TBA8[{Zn2W(O)O3}2H4{α-SiW9O33}2]·5H2O (α-Zn4; TBA = tetra-n-butylammonium) and TBA8[{Zn2W(O)O3}2H4{β-SiW9O33}2]·7H2O (β-Zn4), were synthesized by the solid-state thermally induced isomerization of metastable TBA8[{Zn(OH2)(μ3-OH)}2{Zn(OH2)2}2{γ-HSiW10O36}2]·9H2O (γ-Zn4). Compounds α-Zn4 and β-Zn4 consisted of two [SiW9O33]8− subunits sandwiching the unprecedented distorted hexaprismane core [{Zn2W(O)O3}2]4+

Conceptual Design of Heterogeneous Oxidation Catalyst: Copper Hydroxide on Manganese Oxide-Based Octahedral Molecular Sieve for Aerobic Oxidative Alkyne Homocoupling

The supported copper hydroxide catalyst on manganese oxide-based octahedral molecular sieve OMS-2 (Cu(OH)x/OMS-2) was designed on the basis of the concept of coupled electron transfer. OMS-2 could act as not only a support for copper hydroxide species but also an electron-transfer mediator (cocatalyst) to generate a rapid electron-transfer path from an alkyne to dioxygen. As a result, Cu(OH)x/OMS-2 showed high catalytic performance (TOF = 540 h–1, total TON = 666, and selectivity >99%) and long life (13 times reuse) for aerobic oxidative alkyne homocoupling

Aerobic Oxidative Transformation of Primary Azides to Nitriles by Ruthenium Hydroxide Catalyst

In the presence of an easily prepared supported ruthenium hydroxide catalyst, Ru(OH)x/Al2O3, various kinds of structurally diverse primary azides including benzylic, allylic, and aliphatic ones could be converted into the corresponding nitriles in moderate to high yields (13 examples, 65–94% yields). The gram-scale (1 g) transformation of benzyl azide efficiently proceeded to give benzonitrile (0.7 g, 90% yield) without any decrease in the performance in comparison with the small-scale (0.5 mmol) transformation. The catalysis was truly heterogeneous, and the retrieved catalyst could be reused for the transformation of benzyl azide without an appreciable loss of its high performance. The present transformation of primary azides to nitriles likely proceeds via sequential reactions of imide formation, followed by dehydrogenation (β-elimination) to produce the corresponding nitriles. The Ru(OH)x/Al2O3 catalyst could be further employed for synthesis of amides in water through the transformation of primary azides (benzylic and aliphatic ones) to nitriles, followed by sequent hydration of the nitriles formed. Additionally, direct one-pot synthesis from alkyl halides and TBAN3 (TBA = tetra-n-butylammonium) could be realized with Ru(OH)x/Al2O3, giving the corresponding nitriles in moderate to high yields (10 examples, 64–84% yields)

Transition-Metal-Free Catalytic Formal Hydroacylation of Terminal Alkynes

Although hydroacylation is a very useful reaction for producing ketones from aldehydes with 100% atom efficiency, classical Rh-catalyzed hydroacylation presents several problems, including the need for transition metal catalysts, unwanted decarbonylation of aldehydes, and difficulty in regioselectivity control. However, formal hydroacylation utilizing the nucleophilicity of terminal alkynes can avoid these problems. In this work, we have achieved transition-metal-free formal hydroacylation of terminal alkynes using an Mg3Al–CO3-layered double hydroxide as a heterogeneous catalyst. This system was applicable to the efficient synthesis of α,β-unsaturated ketones with various substituents, and the catalyst can be reused without a significant loss of catalytic performance

Copper-Catalyzed Oxidative Cross-Coupling of <i>H</i>‑Phosphonates and Amides to <i>N</i>‑Acylphosphoramidates

A simple combination of copper(II) acetate (Cu(OAc)₂) and an appropriate base could promote oxidative cross-coupling of <i>H</i>-phosphonates and amides using air as a terminal oxidant. The substrate scope was broad with respect to both dialkyl <i>H</i>-phosphonates and nitrogen nucleophiles (including oxazolidinone, lactam, pyrrolidinone, urea, indole, and sulfonamide derivatives), giving the corresponding P–N coupling products in moderate to high yields

Sandwich-Type Zinc-Containing Polyoxometalates with a Hexaprismane Core [{Zn₂W(O)O₃}₂]⁴⁺ Synthesized by Thermally Induced Isomerization of a Metastable Polyoxometalate

Two novel sandwich-type silicotungstates, TBA8[{Zn2W(O)O3}2H4{α-SiW9O33}2]·5H2O (α-Zn4; TBA = tetra-n-butylammonium) and TBA8[{Zn2W(O)O3}2H4{β-SiW9O33}2]·7H2O (β-Zn4), were synthesized by the solid-state thermally induced isomerization of metastable TBA8[{Zn(OH2)(μ3-OH)}2{Zn(OH2)2}2{γ-HSiW10O36}2]·9H2O (γ-Zn4). Compounds α-Zn4 and β-Zn4 consisted of two [SiW9O33]8− subunits sandwiching the unprecedented distorted hexaprismane core [{Zn2W(O)O3}2]4+

Layered Assemblies of a Dialuminum-Substituted Silicotungstate Trimer and the Reversible Interlayer Cation-Exchange Properties

Two polyoxometalate assemblies, TBA9[{γ-H2SiW10O36Al2(μ-OH)2(μ-OH)}3] (1; TBA = tetra-n-butylammonium) and TBA6Li3[{γ-H2SiW10O36Al2(μ-OH)2(μ-OH)}3]·18H2O (2), were synthesized by trimerization of a dialuminum-substituted silicotungstate monomer. Both 1 and 2 possessed a layered structure composed of a basal sheet unit [TBA3{γ-H2SiW10O36Al2(μ-OH)2(μ-OH)}3]6– and interlayer cations. The interconversion between 1 and 2 reversibly took place through interlayer cation exchange

Efficient Heterogeneous Oxidation of Alkylarenes with Molecular Oxygen

Ru(OH)x/Al2O3 efficiently catalyzes the heterogeneous aerobic oxygenation or oxidative dehydrogenation of alkylarenes to give the corresponding oxygenated or dehydrogenated products. Catalyst/product separation is very easy, and the recovered catalyst is reusable with retention of the high catalytic performance