Contribution to the habit of hydrothermally grown corundum

The growth of corundum crystals without the influence of extraneous ions was achieved by the treatment of single crystals of topaz with supercritical water. The result is in agreement with previous calculations and considerations of other authors. A review of the different indexation of the corundum lattice is given.     

Synthesis and characterization of water-soluble palladium(II)-functionalized diphosphine complexes

Water-soluble functionalized bis(phosphine) ligands L (a–h) of the general formula CH₂(CH₂PR₂)₂, where for a: R = (CH₂)₆OH; b–g: R = (CH₂)_nP(O)(OEt)₂, n = 2–6 and n = 8; h: R = (CH₂)₃NH₂ ( Scheme 1), have been prepared photochemically by hydrophosphination of the corresponding 1-alkenes with H₂P(CH₂)₃PH₂. Water-soluble palladium complexes cis-[Pd(L)(OAc)₂] (1–8) were obtained by the reaction of Pd(OAc)₂ with the ligands a–h in a 1:1 mixture of dichloromethane:acetonitrile. The water-soluble phosphine ligands and their palladium complexes were characterized by IR, ¹H and ³¹P NMR. A crystallographic study of complex 1 shows that the Pd(II) ion has a square planar coordination sphere in which the acetate ligands and the diphosphine ligand deviate by less than 0.12 Å from ideal planar.     

Lattice Points in Three-Dimensional Convex Bodies with Points of Gaussian Curvature Zero at the Boundary

 In this article we investigate the number of lattice points in a three-dimensional convex body which contains non-isolated points with Gaussian curvature zero but a finite number of flat points at the boundary. Especially, in case of rational tangential planes in these points we investigate not only the influence of the flat points but also of the other points with Gaussian curvature zero on the estimation of the lattice rest. Received 19 June 2001; in revised form 17 January 2002 RID="a" ID="a" Dedicated to Professor Edmund Hlawka on the occasion of his 85th birthday     

Quasicrystalline epitaxial single element monolayers on icosahedral Al-pd-mn and decagonal Al-ni-co quasicrystal surfaces

Single element quasicrystalline monolayers were prepared by deposition of antimony and bismuth on the fivefold surface of icosahedral Al71.5Pd21Mn8.5 and the tenfold surface of decagonal Al71.8Ni14.8Co13.4. Elastic helium atom scattering and low energy electron diffraction of the monolayers show Bragg peaks at the bulk derived positions of the clean surfaces, revealing highly ordered quasicrystalline epitaxial films. Their adatom densities of (0.9+/-0.2)x10(15) cm(-2) and (0.8+/-0.2)x10(15) cm(-2) on Al-Pd-Mn and Al-Ni-Co, respectively, correspond to roughly one adatom per Al atom of the quasicrystalline substrate surfaces.     

X-ray absorption and X-ray photoelectron spectroscopy of a rhodium colloid

Transition metal colloids are potential precursors of heterogeneous catalysts with application to selective chemical reactions. Sample preparation techniques are described. Experimental details are given of the characterization of these often air-sensitive particles by X-ray photoelectron and X-ray absorption spectroscopy. First results obtained with both techniques for a Rh-colloid show that the metal is mainly present in the zerovalent chemical state. But the spectra indicate further chemical states of Rh which can be assigned to the outermost metal atoms of the colloid interacting with organic ligands or to the educt Rh-halides.     

η3-Allyl[1,2-bis(diphenylphosphino)ethan]tricarbonylvanadium(0)-komplexe

The preparation, properties and spectroscopic investigation (IR, ¹H NMR, ³¹P NMR, MS) of η³-allyl[1,2-bis(diphenylphosphino)ethan]tricarbonylvanadium(0) compounds are reported.