Olefin epoxidations in the ionic liquid [C4mim][PF6] catalysed by oxodiperoxomolybdenum species in situ generated from molybdenum trioxide and urea–hydrogen peroxide: The synthesis and molecular structure of [Mo(O)(O2)2(4-MepyO)2]·H2O

Commercially available molybdenum(VI) compounds, including molybdenum trioxide, were successfully employed as catalyst precursors in the epoxidation of olefins with urea–hydrogen peroxide adduct (UHP) in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, [C₄mim][PF₆]. After oxidation, the corresponding epoxides were isolated by extraction with diethyl ether. Additionally the ionic liquid–catalyst mixture was recycled and reused in further catalytic cycles. The catalytic species is assumed to be an oxodiperoxomolybdenum species which forms in situ. A representative complex of this type was thus isolated and characterised. Reaction of excess 4-methylpyridine-1-oxide (4-MepyO) with MoO₃ dissolved in aqueous hydrogen peroxide afforded [Mo(O)(O₂)₂(4-MepyO)₂]·H₂O (1) as yellow crystals. Compound 1, an active epoxidation catalyst, was subsequently characterised and its structure determined by X-ray crystallography.     

A combinatorial perspective on the non-Radon partitions

Let E be a finite set of points in $\text{R}$^d. Then {A, E ? A} is a non-Radon partition of E iff there is a hyperplane H separating A strictly from E?A. Or equivalently iff ${}_{\mathrm{<mtext>A</mtext>}}\text{O}$ is an acyclic reorientation of (M_Aff(E), O), the oriented matroid canonically determined by E. If (M(E), O) is an oriented matroid without loops then the set $\text{NR(E, O) = {(A, E ? A):}{}_{\mathrm{<mtext>A</mtext>}}\text{O}\text{is acyclic}\text{}}$ determines (M(E), O). In particular the matroidal properties of a finite set of points in $\text{R}$^d are precisely the properties which can be formulated in non-Radon partitions terms. The Möbius function of the poset $\text{A = {A: A ? E,}{}_{\mathrm{<mtext>A</mtext>}}\text{O}\text{is acyclic}\text{}}$ and in a special case its homotopy type are computed. This paper generalizes recent results of P. Edelman (A partial order on the regions of $\text{R}$ⁿ dissected by hyperplanes     

Des anomalies observées dans l'etude par effet Raman de La2(SO4)3. 9H2O monocristallin en fonction de la temperature

In this paper we present some new results obtained by Raman spectrometry in La₂(SO₄)₂. 9H₂O single crystal. Several particular structural and dynamic properties as well as the anomalies observed near 260 K are reported.     

Euler's relation,möbius functions and matroid identities

We give a short combinatorial proof of the Euler relation for convex polytopes in the context of oriented matroids. Using counting arguments we derive from the Euler relation several identities holding in the lattice of flats of an oriented matroid. These identities are proven for any matroid by Möbius inversion.     

Synthese et caracteristiques spectrales de f-alkyl-2 dihydro-3, 4 oxo-4 quinazolines

In this paper, we report the preparation of a series of 4(3H) quinazolinones substituted in the 2 position by a linear perfluoroalkyl-chain with R_Fas C_n F_2n+1(n=1, 3, 5, 7).These compounds are obtained in two steps, action of F-acid chlorides on 2-aminobenzonitrile which affords the corresponding F-amides followed by cyclization of this intermediate with alkaline hydrogen peroxide. We isolated a reaction intermediate in the cyclization of N-(2-cyanophenyl) F-octanamide. All compounds were identified by the usual spectroscopic methods (IR, NMR¹H, ¹⁹F, mass spectrometry).