Recent Advances in the Catalytic Applications of Lanthanide-Oxo Clusters

Lanthanide-oxo/hydroxo clusters (LOCs) in this mini-review refer to polynuclear complexes featuring a polyhedral metal-oxo/hydroxo cluster core of lanthanide ions exclusively or with coexisting 3d metal ions. We summarize herein the recent works using this unique family of cluster complexes for catalysis; this aspect of research stands in stark contrast to their extensively studied synthetic and structural chemistry as well as the much-researched magnetic properties. Following a brief introduction of the synthetic strategies for these clusters, pertinent results from available literature reports are surveyed and discussed according to the types of catalyzed reactions. Particular attention was paid to the selection of a cluster catalyst for a specific type of reactions as well as the corresponding reaction mechanism. To the end, the advantages and challenges in utilizing LOCs as multifunctional catalysts are summarized, and possible future research directions are proposed.

Catalytic Oxidations with Meta-Chloroperoxybenzoic Acid (m-CPBA) and Mono- and Polynuclear Complexes of Nickel: A Mechanistic Outlook

Selective catalytic functionalization of organic substrates using peroxides as terminal oxidants remains a challenge in modern chemistry. The high complexity of interactions between metal catalysts and organic peroxide compounds complicates the targeted construction of efficient catalytic systems. Among the members of the peroxide family, m-chloroperoxybenzoic acid (m-CPBA) exhibits quite complex behavior, where numerous reactive species could be formed upon reaction with a metal complex catalyst. Although m-CPBA finds plenty of applications in fine organic synthesis and catalysis, the factors that discriminate its decomposition routes under catalytic conditions are still poorly understood. The present review covers the advances in catalytic C–H oxidation and olefine epoxidation with m-CPBA catalyzed by mono- and polynuclear complexes of nickel, a cheap and abundant first-row transition metal. The reaction mechanisms are critically discussed, with special attention to the O–O bond splitting route. Selectivity parameters using recognized model hydrocarbon substrates are summarized and important factors that could improve further catalytic studies are outlined.

Alcohol Oxidation Assisted by Molybdenum Hydrazonato Catalysts Employing Hydroperoxide Oxidants

Molybdenum(VI) catalysts were obtained from methanol or acetonitrile by the reaction of [MoO2(C5H7O2)2] and isonicotinoyl- or nicotinoyl-based aroylhydrazones. Reactions in methanol resulted in the formation of the mononuclear complexes [MoO2(L1–4)(MeOH)] (1a–4a), while the ones in acetonitrile provided polynuclear complexes [MoO2(L1–4)]n (1–4). Crystals of polynuclear compound, [MoO2(L3)]n∙H2O (3∙H2O), suitable for X-ray diffraction analysis were obtained by the solvothermal procedure at 110 °C. Complexes were characterized by infrared spectroscopy (IR-ATR), nuclear magnetic resonance (NMR), elemental analysis (EA), and thermogravimetric analysis (TGA). The prepared catalysts were tested in alcohol oxidation reactions. Carveol, cyclohexanol, and butan-2-ol were investigated substrates. Because the alcohol oxidations are very challenging due to various possible pathways, the idea was to test different oxidants, H2O2, TBHP in water and decane, to optimize the researched catalytic system.

Oxidation of Organic Compounds with Peroxides Catalyzed by Polynuclear Metal Compounds

The review describes articles that provide data on the synthesis and study of the properties of catalysts for the oxidation of alkanes, olefins, and alcohols. These catalysts are polynuclear complexes of iron, copper, osmium, nickel, manganese, cobalt, vanadium. Such complexes for example are: [Fe2(HPTB)(m-OH)(NO3)2](NO3)2·CH3OH·2H2O, where HPTB-¼N,N,N0,N0-tetrakis(2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane; complex [(PhSiO1,5)6]2[CuO]4[NaO0.5]4[dppmO2]2, where dppm-1,1-bis(diphenylphosphino)methane; (2,3-η-1,4-diphenylbut-2-en-1,4-dione)undecacarbonyl triangulotriosmium; phenylsilsesquioxane [(PhSiO1.5)10(CoO)5(NaOH)]; bi- and tri-nuclear oxidovanadium(V) complexes [{VO(OEt)(EtOH)}2(L2)] and [{VO(OMe)(H2O)}3(L3)]·2H2O (L2 = bis(2-hydroxybenzylidene)terephthalohydrazide and L3 = tris(2-hydroxybenzylidene)benzene-1,3,5-tricarbohydrazide); [Mn2L2O3][PF6]2 (L = 1,4,7-trimethyl-1,4,7-triazacyclononane). For comparison, articles are introduced describing catalysts for the oxidation of alkanes and alcohols with peroxides, which are simple metal salts or mononuclear metal complexes. In many cases, polynuclear complexes exhibit higher activity compared to mononuclear complexes and exhibit increased regioselectivity, for example, in the oxidation of linear alkanes. The review contains a description of some of the mechanisms of catalytic reactions. Additionally presented are articles comparing the rates of oxidation of solvents and substrates under oxidizing conditions for various catalyst structures, which allows researchers to conclude about the nature of the oxidizing species. This review is focused on recent works, as well as review articles and own original studies of the authors.

Speciation and Separation of Platinum(IV) Polynuclear Complexes in Concentrated Nitric Acid solutions

Understanding the solution chemistry of Pt(IV) is crucial for the hydrometallurgy of precious metals. To gain such an understanding, the speciation and separation of Pt(IV) complexes in concentrated HNO3 solutions...

Spotlighting main group elements in polynuclear complexes

François Gabbaï, Cameron Jones and Connie Lu introduce the Chemical Science themed collection on the topic of main group elements in polynuclear complexes.

Strength Study of Sorption Composites Based on Microfine Glass Fibers

Исследуется влияние минерального и органического связующего на термостойкость и показатель разрушающего усилия композиционных сорбционных материалов на основе стеклянных волокон. Рассматриваемый материал используется для сорбции органических соединений при низких концентрациях. Изучение влияния на эти два показателя вызвано тем, что материал, описываемый в настоящей статье, требует определенной технологической прочности и должен выдерживать температуры 300 °С. Для достижения требуемых параметров для материала исследовались три типа связующего: 1. Полиядерные комплексы алюминия, полученные в результате гидролиза хлорида алюминия; 2. Полиядерные комплексы алюминия, полученные в результате гидролиза сульфата алюминия; 3. Сульфатная небеленая целлюлоза. По результатам исследования было выявлено наиболее подходящее связующее для сорбционного композиционного материала и определено оптимальное процентное содержание этого связующего. Discusses the influence of mineral and organic binders on the heat resistance and the index of the destructive force of composite sorption materials based on glass fibers. This material is used for sorption of organic compounds at low concentrations. Consideration of the impact on these two indicators is caused by the fact that the material described in this article requires a certain technological strength and must withstand temperatures of 300 °C. To achieve the required parameters for the material, three types of binder were studied: 1. Polynuclear complexes of aluminium, obtained by hydrolysis with aluminium chloride; 2. Polynuclear complexes of aluminium, obtained by hydrolysis of aluminium sulfate; 3. Sulfate unbleached cellulose. According to the results of the study, the most suitable binder for the sorption composite material was identified and the optimal percentage of this binder was determined.

Effect of the content and type of binder on the strength of glass fiber paper

Проведено исследование композиционного материала на основе минерального волокна с использованием в качестве связующего полиядерных комплексов металлов. Новизной и особенностью данного исследования является использование в качестве связующего для композиционного материала на основе стеклянных волокон полиядерных комплексов титана. Добавление связующего на основе полиядерных комплексов в композицию целесообразно в интервале 5–30% от массы волокна. Исследованный композиционный материал с добавлением в качестве связующего полиядерных комплексов титана имеет прочностные характеристики при рН отлива 10 и 12 выше, чем у материалов с добавлением полиядерных комплексов алюминия и обладает достаточной технологической прочностью. Полиядерные комплексы титана можно использовать как перспективные связующие для композиционных фильтровальных материалов на основе стеклянных волокон. The study of composite material based on mineral fiber using polynuclear metal complexes as a binder was carried out. The novelty and feature of this study is the use of polynuclear complexes of titanium as a binder for a composite material based on glass fibers. Adding a binder based on polynuclear complexes to the composition is advisable in the range of 5-30% by weight of the fiber. The studied composite material with the addition of polynuclear complexes of titanium as a binder has strength characteristic at pH levels 10 and 12, higher, than that of materials with the addition of polynuclear complexes of aluminum and has sufficient technological strength. Polynuclear complexes of titanium can be used as promising binders for composite filter materials based on glass fibers.