Titanocene-Catalyzed Reduction of Lactones to Lactols

A convenient method for the conversion of lactones to lactols is described. The hydrosilylation to lactols is carried out via air-stable titanocene difluoride or a titanocene diphenoxide precatalyst using inexpensive polymethylhydrosiloxane (PMHS) as the stoichiometric reductant. These procedures have been demonstrated with a variety of substrates and proceed in good to excellent yield.     

X-ray absorption spectroscopy of the 90K superconductor YBa2Cu3O7−δ

X-ray absorption spectroscopy has been used to probe the Cu environment of the new highT _c YBa₂Cu₃O_7– superconductor. Evidences of other valencies than two are found for copper. Besides Cu¹⁺ which is localized on Cu₁ sites when the unit cell is oxygendeficient, one invokes a ground state which merges bivalent 3d ⁹ to 3d ⁹ L configurations as proposed in a recent paper (L stands for a ligand hole in the CuO bond) very similar to that observed in many light rare earth oxides.     

Alkali halide nanocrystal growth and etching studied by AFM and modeled by MD simulations

NaCl hillocks have been grown on the NaCl(100) monocrystalline surface by simply making the tip of an atomic force microscope cantilever interact with the surface. A quantitative discussion about the hillock dissolution process as well as physical stability of these ionic surfaces has been made. Molecular dynamics simulations helped us to interpret the experimental data. An explanation for the hillock formation and dissolution phenomena is also discussed.     

Ferromagnetic coupling between low- and high-spin iron(III) ions in the tetranuclear complex fac-[[FeIII[HB(pz)3](CN)2(mu-CN)]3FeIII(H2O)3]* 6H2O ([HB(pz)3]- = hydrotris(1-pyrazolyl)borate)

The novel mononuclear PPh4-fac-[FeIII[HB(pz)3](CN)3]*H2O (1) [PPh4+= tetraphenylphosphonium cation; (HB(pz)3)- = hydrotris(1-pyrazolyl)borate] and tetranuclear fac-[[FeIII[HB(pz)3](CN)2(mu-CN)]3FeIII(H2O)3]*6H2O (2) have been prepared and characterized by X-ray diffraction analysis. Crystal data for compound 1: monoclinic, space group P21/c, a = 9.575(3) A, b = 21.984(4) A, c = 16.863(3) A, beta = 100.34(2) degrees, U = 3486(1) A3, Z = 4. Crystal data for compound 2: orthorhombic, space group Pnam, a = 14.084(3) A, b = 14.799(4) A, c = 25.725(5) A, U = 5362(2) A3, Z = 4. Compound 1 is a low-spin iron(III) compound with three cyanide ligands in fac arrangement and a tridentate pyrazolylborate ligand building a distorted octahedral environment around the iron atom. Compound 2 is the first example of a molecular species containing three peripheral low-spin iron(III) ions linked to a central high-spin iron(III) cation by single cyanide bridges, the anion of 1 acting as a monodentate ligand in 2. Variable-temperature magnetic susceptibility measurements of 2 reveal the occurrence of a significant ferromagnetic coupling between the three peripheral low-spin iron(III) centers and the central high-spin iron(III) ion cations leading to a low-lying nonet spin state.