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The benzannulated spiroketal cores (IV) of berkelic acid are readily produced by Horner—Wadsworth—Emmons olefination and a one-pot hydrogenation/deprotection/cyclization process.

A strategy for the synthesis of benzannulated spiroketals through oxidative radical cyclization is described.

Stable nanosized particles of niobium and tantalum oxides were obtained by hydrolysis of the metal ethoxides in ethanol with triethylamine. These sols were amorphous hydrated oxides M2O5·nH2O. They were used to prepare thin porous films on SiO2 disks via spin-coating techniques. These coatings displayed thicknesses ranging from 100 to 300 nm and a refractive index of about 1.7. Laser damage tests at 1053-nm wavelength with a pulse duration of 3 ns were conducted on the single-layer systems. Ta2O5 coatings exhibited much higher threshold values (averaging 14.5 ± 2.1 J/cm2) than those of Nb2O5 (averaging 8.3 ± 1.6 J/cm2). Buildup of multilayer stacks of high- and low-index materials was prevented because of internal stress.

Single-components or multicomponent oxide thin films are of interest for electronic and opto-electronic devices, optical applications, catalysis, corrosion protection etc. Their preparation by chemical routes is based on the hydrolytic (sol-gel process) or pyrolytic (MOCVD) conversion of precursors. Derivatives having MO bonds, namely metal alkoxides, carboxylates or β-diketonates, are the most common sources of metal oxides. The properties of alkoxides are appropriate for sol-gel as well as MOCVD applications, whilst the limited hydrolytic susceptibility but good volatility of β-diketonates is most convenient for MOCVD purposes. The low temperature and flexibility of sol-gel routes, and the presence of residual OH groups in the final films, are favorable for the encapsulation of organic or organometallic derivatives, the anchoring of enzymes and in general for the development of functional and composite coatings. The facile formation of heterometallic alkoxides is also attractive for the development of coatings based on multimetallic formulations. MOCVD is favorable for the buildup of heterostructures and epitaxial layers. Although metal alkoxides and β-diketonates are usually oxide precursors, nitride or sulfide films can be obtained by reacting with the appropriate reagents. Fluorinated ligands enhance volatility but often result in the formation of metal fluorides.

The high coordination numbers required by large elements (Ln, Ba...) favor the formation of closo oxo aggregates by desolvation of M(OR)n(ROH)x solvates and subsequent non-hydrolytic condensation. Pentanuclear M5O cores display a remarkable stability for large elements and can associate along an edge or an apex. Heteronuclear arrays are thus accessible from these aggregates by Lewis acid-base reactions or, for a better control of stoichiometry between the metals, by reactivity of the coordinated alcohol of a solvate. Functionalisation by polymerisable O-donors such as allylacetatoacetate (HAAA) provides species which can be converted into organic-inorganic arrays by copolymerisation reactions.

This critical review deals with the chemistry and applications of metal alkanoates with medium size (C5 to C12) carbon chain length. A particular emphasis is given to metal 2-ethylhexanoates, which find wide applications as metal–organic precursors in materials science, as catalysts for ring opening polymerizations and also in painting industries for their properties as driers. After a brief introduction and an overview of synthesis, structural and physico-chemical properties, this article discuses extensively the applications of these compounds in materials science. Finally, it identifies and signifies the areas for future research in the looking ahead section. The aim of this review is to bridge the areas of precursor's chemistry and materials science by providing a reference text for researchers working either in or at the interface of these two areas (125 references).

Reaction between Y5O(OiPr)13 and acetylacetone at room temperature under anhydrous conditions, produced in high, reproducible yield a compound characterized—by 1H and 13 C NMR, as well as X-ray diffraction—as Y2(μ2-OAc)2(acac)4(H2O)2. It crystallizes in the orthorhombic Pcnb system, with unit cell dimensions a = 13.385 (3), b = 15.107(4), c = 16.100(4) A and Z = 4. Least-squares refinement converged to a final R = 0.0356. The molecule is a centrosymmetric dimer with chelating tridentate acetato groups in the bridging positions. The yttrium atoms are eight-coordinated, with a distorted square antiprism geometry. Intra- as well as intermolecular hydrogen bonding between the water molecules and the β-diketonato ligands is observed. The formation of this acetatoacetylacetonate derivative as well as its behaviour in solution are discussed.

The two products were characterized by elemental analysis, molecular weight data, IR and NMR spectroscopy. [Pb(OBu t ) 2 ] 2 and Pb 4 O(OBu t ) 6 are white air-sensitive solids, both highly soluble in the unual solvents, including hexane

Reaction between neodymium chips and isopropanol led to the isolation of [Nd(OiPr)3]4·4iPrOH. Its desolvation results in a soluble polynuclear neodymium(III) oxoisopropoxide, whose reactivity has been investigated. Reaction with acetylacetone produced a compound analysing as Nd2(OH)(acac)5, which has been characterized by IR and ESR spectroscopy, as well as by X-ray diffraction. It crystallizes in the monoclinic P 21/n system with unit cell dimensions α = 14.52(5), b = 14.20(4), c = 15.25(5) A, β = 101.4° and Z = 4. Least-squares refinement converged to a final Rw = 0.050. The molecule is a centrosymmetric, tetranuclear neodymium(III) hydroxo acetylacetonate cluster, [Nd4(μ3-OH)2(μ2,μ1-acac)6(acac)4]. Two dinuclear Nd2(OH)(acac)5 units are linked by two triply bridging pyramidal μ-hydroxo ligands and by two bridging-chelating β-diketonate ligands. The metal atoms are eight-coordinated with a distorted square antiprism geometry.

Les composes [M(OR) n ] m sont des precurseurs de choix pour les oxydes de haute purete et des materiaux a haute performance, par voie chimique, hydrolyse suivie de reactions de polycondensation ou pyrolyse. Ce sont egalement de bons produits pour l'obtention de nouveaux materiaux catalytiques