Intramolecular reduction of the nitro group into phosphoraneimine mediated by a rhenium(v) complex. Synthesis and structure of the novel phosphoraneimine oxorhenium(v) complex [ReOCl[o-(PPh3=N)C6H4(NCH2CH2N(CH2CO2H)CH2CO2]

The title compound was synthesised via an unexpected intramolecular reduction of a nitro group in the oxo-Re(v) coordination sphere.     

Advances in electric field and atomic surface derived properties from experimental electron densities

The present study is devoted to a general use of the Gauss law. This is applied to the atomic surfaces derived from the topological analysis of the electron density. The method proposed here is entirely numerical, robust and does not necessitate any specific parametrization of the atomic surfaces. We focus on two fundamental properties: the atomic charges and the electrostatic forces acting on atoms in molecules. Application is made on experimental electron densities modelized by the Hansen-Coppens model from which the electric field is derived for a heterogenic set of compounds: water molecule, NO(3) anion, bis-triazine molecule and MgO cluster. Charges and electrostatic forces are estimated by the atomic surface flux of the electric field and the Maxwell stress tensor, respectively. The charges obtained from the present method are in good agreement with those issued from the conventional volume integration. Both Feynman and Ehrenfest forces as well as the electrostatic potential at the nuclei (EPN) are here estimated from the experimental electron densities. The values found for the molecular compounds are presented and discussed in the scope of the mechanics of atomic interactions.     

Topological features of both electron density and electrostatic potential in the bis(thiosemicarbazide)zinc(II) dinitrate complex

The experimental electron density of the bis(thiosemicarbazide)zinc(II) dinitrate complex, [Zn(CH5N3S)2](NO3)2,was studied. The Hansen-Coppens multipole model was used to extract the electron density from high-resolution X-ray diffraction data collected at 100 K. Careful strategies were designed for the electron density refinements regarding the charge transfer between the anionic and the cationic parts of the complex. Particular attention was also paid to the treatment of the electron density of the zinc atom interacting with two thiosemicarbazide ligands in a tetrahedral coordination. Nevertheless, the filled 3d valence shell of Zn was found unperturbed, and only the 4s shell was engaged in the metal-ligand interaction. Topological properties of both electron density and electrostatic potential, including kinetic and potential energy densities, and atomic charges were reported to quantify a metal-ligand complex with particular Zn-S and Zn-N bonds and hydrogen-bonding features. Chemical activities were screened through the molecular surface on which the three-dimensional electrostatic potential function was projected. The experimental results were compared to those obtained from gas-phase quantum calculations, and a good agreement was reached between these two approaches. Finally, among other electrostatic potential critical points, the values at the maxima corresponding to the nuclear sites were used as indices of the hydrogen-bonding capacity of the thiosemicarbazide ligand.     

Finite volume approximation of degenerate two‐phase flow model with unlimited air mobility

Models of two‐phase flows in porous media, used in petroleum engineering, lead to a coupled system of two equations, one elliptic and the other degenerate parabolic, with two unknowns: the saturation and the pressure. In view of applications in hydrogeology, we construct a robust finite volume scheme allowing for convergent simulations, as the ratio μ of air/liquid mobility goes to infinity. This scheme is shown to satisfy a priori estimates (the saturation is shown to remain in a fixed interval, and a discrete L2(0,T;H1(Ω)) estimate is proved for both the pressure and a function of the saturation), which are sufficient to derive the convergence of a subsequence to a weak solution of the continuous equations, as the size of the discretization tends to zero. We then show that the scheme converges to a two‐phase flow model whose limit, as the mobility of the air phase tends to infinity, is the “quasi‐Richards equation” (Eymard et al., Convergence of two phase flow to Richards model, F. Benkhaldoun, editor, Finite Volumes for Complex Applications IV, ISTE, London, 2005; Eymard et al., Discrete Cont Dynam Syst, 5 (2012) 93–113), which remains available even if the gas phase is not connected with the atmospheric pressure. Numerical examples, which show that the scheme remains robust for high values of μ, are finally given. © 2012 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2013     

[PMe3(CH2CH(OMe)Ph)]+ A PHOSPHONIUM SALT WITH AN ASYMMETRIC CARBON ATOM SYNTHESIZED BY REACTION OF PHENYLACETYLENE WITH COBr(PMe3)3 IN METHANOL. STRUCTURAL CHARACTERIZATION

Abstract

Reaction of HC[tbnd]CPh in excess with a mixture of CoBr(PMe₃)₃/NaBPh₄ in methanol gave rise in 40% yield to the cationic phosphonium salt [PMe₃(CH₂CH(OMe)Ph)]BPh₄. It has been characterized in the solid state by X-ray diffraction and in solution by ¹H and ³¹P NMR.     

Design and synthesis of new ethylenediamine or propylenediamine diacetic acid derivatives for Re(I) organometallic chemistry

A general synthetic approach for a novel range of bifunctional chelating agent (BCA) for the ‘fac-[M(CO)₃]⁺‘ core (M=^99mTc, ⁹⁹Tc or Re) has been developed. The strategy includes the facile preparation of these tridentate ligands possessing a tertiary amine bearing two carboxylic acid functions as coordinating site and an aromatic amino group for coupling to a biovector. First complexation study has shown that these compounds act exclusively as tridentate ligands (via the two acids and the tertiary amine functions). The convenient synthesis of these new ligands coupled with their high affinity for Re(I) make them quite promising for biomedical applications.