Cleavage of selenoacetals by clay-supported metal nitrates

Bis(methylseleno)acetals and bis(phenylseleno)acetals are cleaved into aldehydes or ketones, under very mild conditions, by K10 clay-supported ferric or cupric nitrate.     

Novel nitration of estrone by metal nitrates

Nitration of estrone has been investigated with different types of metal salts in the presence of solid surfaces under various conditions.     

Thermal decomposition of metal nitrates

The paper presents a study regarding the preparation of 40 %M^IIFe₂O₄/60 %SiO₂ nanocomposites (M = Ni, Zn, Cu) by thermal decomposition of metal nitrates—poly(vinyl alcohol)–tetraethyl orthosilicate gels. Thermal analysis and FT-IR spectroscopy have evidenced that a redox reaction takes place between PVA and NO ₃ ^? ions in the pores of the formed hybrid gels. The result of this redox reaction is the formation of carboxylate-type coordination compounds that have the role of a precursor of the ferrite nanoparticles. By thermal decomposition of these precursors inside the silica matrix, the corresponding MFe₂O₄/SiO₂ nanocomposites are obtained starting with 600 °C, as resulting from XRD analysis. Elemental maps of the corresponding involved elements M (Ni, Zn, Cu), Fe, and Si have confirmed the homogenous distribution of the ferrite nanoparticles within the silica matrix. TEM images have shown that the nanocomposites were obtained as fine nanoparticles, with diameter up to 20 nm. All nanocomposites 40 %M^IIFe₂O₄/60 %SiO₂ obtained at 1000 °C presented magnetic properties characteristic to this type of nanocomposite.     

Synthesis of 2-arylbenzimidazoles catalyzed by transition metal nitrates

A simple and practical procedure for synthesis of 2-arylbenzimidazoles by a one-pot condensation of o-phenylenediamine with aromatic aldehydes in the presence of a catalytic amount of M(NO₃)₂·6H₂O (M = Mn, Fe, Co, Ni, Cu) in ethanol at room temperature is described. Major advantages of this practical procedure are use of a readily available catalyst, high yields, short reaction times, and simplicity of the reaction and workup.     

Oxidation of alcohols by metal nitrates supported on silica gel

Many metal nitrates, especially zinc(II) and copper(II) nitrates, supported on silica gel, oxidized secondary and benzylic alcohols to the corresponding ketones and aldehydes efficiently.     

Cleavage of cyclopropene ring by means of transition metal salts

The oxidative ring cleavage of 1,3,3-trimethylcyclopropene (1) with Hg(OAc)₂ in methylene chloride gives 1,1-diacetoxy-2,3-dimethyl-2-butene (5). The reaction of 1 with TI(OAc)₃ or Pb(OAc)₄ gives in addition to 5, 3,3-diacetoxy-2-methylpropene and 2-acetoxy-4-methyl-1,3-pentadiene. These products are explained by assuming the addition of metal acetates onto the double bond of 1 followed by the ring cleavage to give vinylcarbene-metal acetate complexes or inverse ylides. The reaction of benzocyclopropene (14) with Hg(OAc)₂ affords bis(o-acetoxymethylphenyl)mercury as a single product. Cyclopropene ring cleavage of 14 effected by Cu(II) or Ag(l) acetate furnishes 9,10-dihydrophenanthrene and benzyl acetate. These products are ascribed to the intermediary vinylcarbene- metal acetate complexes produced from 14.     

Lanthanoid metal nitrates with hydrogen bonded hexamethylenetetramine

Cerium, praseodymium, and neodymium nitrate complexes with hydrogen bonded hexamethylenetetramine (HMTA) of the formula [Ce(NO₃)₂(H₂O)₅](HMTA)₂(NO₃)(H₂O)₃, [Pr(NO₃)₂(H₂O)₆]₂[Pr(H₂O)₉](HMTA)₆(NO₃)₆(H₂O)₄ and [Nd(NO₃)₂(H₂O)₅](HMTA)₂(NO₃)(H₂O)₃ have been prepared and characterized by X-ray crystallography. All the complexes belong to monoclinic crystal system. Ce and Nd complexes have P21/n space group, whereas Pr complex has C2/c. Thermal analyses of these complexes were carried out using TG, DSC, which showed their multi-step decomposition. Kinetics of thermolysis has been done by applying model fitting as well as model free isoconversional method. In order to see the response of rapid heating, ignition delay measurements were carried out. The thermal decomposition pathways have also been demonstrated. On the basis of thermal studies the thermal stability of the complexes was found in the order; Pr > Ce > Nd. In order to identify the end products of thermolyses, X-ray diffraction patterns of end product were carried out which showed the formation of corresponding metal oxides.     

Direct thermal decomposition of metal nitrates in octadecylamine to metal oxide nanocrystals

We have developed a method for the synthesis of metal oxide nanocrystals with controllable shape and size, which is based on the direct thermal decomposition of metal nitrates in octadecylamine. Mn3O4 nanoparticles and nanorods with different lengths were synthesized by using manganese nitrate as the decomposition material. Other metal oxide nanocrystals such as NiO, ZnO, CeO2, CoO, and Co3O4 were also prepared by this method. These nanocrystals were then assembled into 3D colloidal spheres by a surfactant-assisted self-assembly process. Subsequently, calcination was carried out to remove the surfactants to obtain mesoporous metal oxides, which show large pores, good crystallization, thermally stable pore mesostructures, and potential applications in various fields, especially in catalysis and lithium-ion batteries.     

Cleavage and isomerization of UpU promoted by dinuclear metal ion complexes

The catalysis of phosphoryl transfer by metal ions has been intensively studied in both biological and artificial systems, but the status of the transient pentacoordinate phosphoryl species (as transition state or intermediate) is the subject of considerable debate. We report that dinuclear metal ion complexes that incorporate second sphere hydrogen bond donors not only promote the cleavage of RNA fragments just as efficiently as the activated analogue HPNPP but also provide the first examples of metal ion catalyzed phosphate diester isomerization close to neutral pH. This observation implies that the reaction catalyzed by these complexes involves the formation of a phosphorane intermediate that is sufficiently long-lived to pseudorotate.     

Model investigation of the polymerization of acrylamide complexes with metal nitrates by ESR

Modelling experiments have shown that the interaction between NO₂ and acrylamide (AA) and the AA complex with calcium nitrate leads to the formation of radical centers. Analogous paramagnetic centers are detected directly in AA complexes with calcium nitrate. The ESR spectrum differs from that of -irradiated AA and is caused by nitroxyl radicals appearing in the course of the consecutive transformations in the system. The data obtained support the earlier suggested mechanism of NO₂-initiated polymerization of acrylamide complexes with metal nitrates.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 534–536, March, 1994.This work was financially supported by the Russian Foundation for Basic Research (project No. 93-03-4162).     

Effects of metal salts on polymerization. Part IV. Polymerization of N-vinylcarbazole initiated by oxidizing metal nitrates

The polymerization of N-vinylcarbazole (VCZ) in ethylene dichloride, acetone, benzene, and dioxane with cupric nitrate, ferric nitrate, and ceric ammonium nitrate as catalyst was studied. In all cases the polymerization seemed to be of a cationic nature, judged by copolymerization with styrene. Electron spin resonance (ESR) spectroscopy was made for the polymerization system and also for a system containing N-ethylcarbazole instead of VCZ. Singlet ESR spectra were observed for all systems containing ceric salt and for some systems containing ferric salt but not for systems containing cupric salt. The ESR spectra indicated the formation of an ion radical by electron transfer between the oxidizing metal salt and the carbazole derivatives. Mechanisms of initiation other than electron transfer were less likely, and it was concluded that the initiation process was most likely to be of the electron transfer type.     

Oxidation of thiols with metal nitrates supported on TAFF

Twelve thiols were readily oxidized to the corresponding disulfides by means of four metal nitrates supported on TAFF, a bentonitic clay, under mild conditions. However, in some cases, thioethers and other interesting by‐products were detected. Some of the disulfides showed antimicotical activities against Aspergillus fumigatus, Aspergillus niger, Aspergillus candidus, Microsporum gypseum, Candida albicans, and Cryptococcus neoformans © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:262–265, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10138     

Cleavage of unreactive bonds with pincer metal complexes

Since the first reports some three decades ago, the chemistry of pincer metal complexes has seen a tremendous development with impact on materials chemistry, supramolecular chemistry, bioorganometallics, and, presumably most significantly, on (catalytic) bond making and breaking processes. The remarkable progress is due to a large extent to the well-defined nature and tunability of the pincer ligand which allows the reactivity of the metal center to be modified and eventually tailored to specific needs. This Perspective summarizes the achievements in employing pincer complexes for mediating and catalyzing the cleavage of typically unreactive bonds such as C-H, C-C, C-E, and E-H bonds, arguably one of the most spectacular applications of pincer chemistry.     

Conversion of n,n-dimethylhydrazones to carbonyl compounds by clay-supported ferric nitrate

Cleavage of N,N-dimethylhydrazones is cleanly effected with good yield in dichloromethane using the extremely inexpensive clay-supported ferric nitrate.     

Transformation of thioacetals to cyclopropanes

Cyclopropanes were obtained by the titanocene(II)-promoted reaction of thioacetals with vinyl pivalate. It was also found that vinycyclopropanes were produced by a similar treatment of thioacetals with the titanocene(II) species in the presence of 1,3-dienes.     

Thiocarbonyls into carbonyls: efficient conversion by clay-supported ferric nitrate

A simple and inexpensive procedure is proposed for achieving the title transformation. The method works best with thiobenzophenones (60–100 % yields).     

Explosive degradation of woody biomass under the presence of metal nitrates

The influence of various metal nitrates (Fe, Ni, Cu, Zn, etc.) has been studied in the pyrolysis of woody biomass under inert atmosphere. Pyrolysis samples have been prepared by impregnation of wood with aqueous solution of the salts as well as by mechanical mixing of powders of wood and nitrates. Thermogravimetric analysis showed that the addition of nickel, copper and zinc nitrates reduced significantly the decomposition temperature of wood below 150 °C. The decomposition of wood completes explosively at the temperature. The pyrolysis products have been analysed by GC–MS and XRD methods. Preliminary result of the quantitative analysis of emitted NO_x gas in the pyrolysis treatment is also presented.     

Oxidation of alcohols using clay-supported potassium peroxodiphosphate

Clay-supported potassium peroxodiphosphate efficiently oxidizes benzylic alcohols to the corresponding aldehydes without overoxidation to acids. H₃P₂O_g ⁻ as the active species.