Yoshinao Oosawa

Preparation of chelate ylide ligands and their palladium(II) and platinum(II) halide complexes

Keto-stabilized mono-ylides of 1,2-bisdiphenylphosphinoethane and bisdiphenylphosphinomethane, Ph2P(CH2)nP+(Ph)2C-HC(O)R (Ph  C6H5; n  1 or 2; R  C6H5, CH3 or OCH3), and their palladium(II) and platinum(II) halide complexes were prepared and characterized by means of infrared, 1H and 31P NMR spectra. The chelate ylide ligands coordinate to the metal through the ylide carbon and phosphine phosphorus forming a six or five-membered chelate ring. The stability of the MC(ylide) bonding is discussed on the basis of the results of the reaction of the complexes with pyridine.

Three Types of Ternary Selenides with Layered Composite Crystal Structures Formed in the Pb-Nb-Se System

Three types of ternary selenides with layered composite crystal structures, (PbSe)1.14NbSe2[A], (PbSe)1.14(NbSe2)2[B] and (PbSe)1.14(NbSe2)3[C], have been prepared and characterized by powder X-ray diffraction, electron diffraction, intercalation and electric resistivity measurement. Results suggest that each selenide consists of PbSe layers(two-atoms-thick) and NbSe2 sandwiches(three-atoms-thick) stacked alternately with the ratios of 1:1 for A, 1:2 for B and 1:3 for C, respectively. Electric resistivity measurements suggest that B and C are superconductors whose transition temperatures are 3.4 K and 4.8 K, respectively.

Crystal chemistry of CuBa2Can−1CunOy( n = 4, 5, 6) superconductors

Abstract The crystal structures of Cu-based superconductors CuxBa2Can−1CunOy and (Cu,C)Ba2Can−1CunOy with n = 4, 5, 6 have been investigated using intensity data collected on the single-crystal X-ray four-circle diffractometer. The Cu-site occupancy x in the deficient Cu(1)O2 sheet between two BaO layers increases from 0.62 to 0.73 accompanied by a decrease in the c-axis length in CuxBa2Ca3Cu4Oy. The thickness of the charge reservoir-layer block decreases with decreasing c-axis length from 8.421(4) A for c = 18.0016(39) A to 8.373(3) A for c= 17.9434(8) A in CuBa2Ca3Cu4Oy, and from 8.405(2) A for c = 21.1546(14) A to 8.34(1) A for c = 21.0784(15) A in CuBa2Ca4Cu5Oy, respectively, while the thickness of the superconducting-layer block unchanged in both series. From the results of the structure refinement and chemical analysis, we propose a general formula (CuxC1−x−δ)Ba2Can−1CunOy for these nonstoichiometric compounds, not only for the CuxBa2Can−1CunOy series but also for the carbonate-containing (Cu,C)Ba2Can−1CunOy compounds, where δ equals the vacancy content in the defect site.

High pressure synthesis and characterization of single crystals of CuBa2Ca3Cu4Oy superconductor

Abstract Single crystals of CuBa 2 Ca 3 Cu 4 O y (Cu-1234) with dimensions up to 200×100×20 μ m 3 have been synthesized under high pressure using a belt type anvil apparatus. The impurity of Au, emanating from Au capsule, was found in the crystals by SEM–EDS analysis. These crystals showed superconducting transition temperature ( T c ) ranging from 105 K to 68 K and are lower than that of Au-free polycrystals ( T c =118 K). The T c values are found to decrease linearly with Au content at a substantially high rate of 7.0±0.4 K%, indicating the substitution of Au ions for Cu-sites. Superconducting anisotropy γ as estimated from the resistivity data of Cu-1234 single crystal just above T c (=102 K) has been found to be higher ( γ =5.8) than that for the Au-free polycrystals.

Preparation of LiTi2O4 single crystals with the spinel structure

Single crystals of the spinel-type LiTi{sub 2}O{sub 4} (Cubic, Fd3m, a = 8.4095(12) {angstrom}) have been prepared by the reaction of lithium metal and TiO{sub 2} at 1373 K in a sealed iron vessel. The structure refinement by a single crystal X-ray diffraction study confirmed a normal spinel cation distribution; the lithium cations are located at the tetrahedral 8a sites, the titanium cations occupy the octahedral 16d sites, and the oxygen parameter u = 0.2622(4) with the final R = 3.8% (R{sub w} = 2.7%) for 60 independent observed reflections. The octahedral Ti-O distance is 2.005(3) {angstrom}, and the tetrahedral Li-O distance is 1.999(3) {angstrom}. The superconductivity for the crystals was observed by the magnetization measurements.

Crystal structure analysis of Cu0.6Ba2Ca3Cu4O10.8 by single-crystal X-ray diffraction method

Abstract The small platelet single crystal of a new 116 K superconducting cuprate having the structural formula Cu 1− x Ba 2 Ca 3 Cu 4 O 12− γ ( x =0.4, y =1.2; Cu-1234) have been synthesized using a high-temperature and high-pressure technique. This compound crystallizes in the tetragonal system, space group P4/mmm with a=3.8526 (18) A and c=17.973 (5) A . The crystal structure was determined from single-crystal X-ray diffraction method and refined to the conventional values R =0.047 and wR =0.032 for unique 278 reflections collected up to 2 θ = 70° with Mo K α radiation. Some weak superlattice spots were also observed by the X-ray precession method. The crystal structure of Cu-1234 can be regarded approximately as an intermediate between the infinite-layered structure and the Tl- or Hg-based 1234 structure. The existence of the deficient CuO 2 sheet between two BaO layers in this compound, instead of a TlO 2 sheet in the Tl-1234 structure, has been confirmed.

Preparation of cationic chelate ylide complexes of palladium(II) and platinum(II)

Abstract Cationic palladium(II) and platinum(II) complexes with chelate ylides and neutral ligands of the type, [MCl (Y) (L)] + BPh 4 − (M  Pd or Pt; Y  bdep or bdmp*; L = 4-methylpyridine, 3,5-dimethylpyrazole, PPh 3 , PCy 3 , PMePh 2 , P(OMe) 3 , AsPh 3 or SbPh 3 ) and [M(bdep) (4-methylpyridine) 2 ] (BPh 4 ) 2 (M = Pd or Pt) were prepared and characterized by means of infrared and 1 H NMR spectra.

Preparation, characterization and intercalation of ternary selenides with layered composite crystal structures formed in the Pb-Nb-Se system

Abstract Three types of ternary selenides with layered composite crystal structures (PbSe) 1.14 NbSe 2 [A], (PbSe) 1.14 (NbSe 2 ) 2 [B] and (PbSe) 1.14 (NbSe 2 ) 3 [C] have been prepared as powder samples. All the samples were characterized by both electron diffraction and X-ray diffraction. A dependence of the products on the preparation temperature and composition has been examined. It has been found that intercalation occurs for the selenides [B] and [C] through the treatment with hydrazine monohydrate. The atomic coordinates in the layer-stacking direction of [B], [C] and their intercalation compounds have been determined on the basis of a Rietveld analysis of the X-ray diffraction profile of 00 l diffraction lines.

Preparation and Characterization of New Sb-Containing Ternary Sulfides with Layered Composite Crystal Structure

New Sb-Containing ternary sulfides with layered composite crystal structure have been prepared and characterized: (SbS)nTiS2, (SbS)nTaS2, (SbS)n(NbS2)2, and (SbS)n(TaS2)2; n1. On the basis of X-ray and electron diffraction patterns, it is suggested that the first and the second sulfides consist of a SbS and a TS2 (T=Ti or Ta) layers stacked alternately and that the third and the fourth sulfides consist of a SbS and two TS2 (T=Nb or Ta) layers stacked alternately. The in-plane electric resistivity of (SbS)nTaS2 showed metallic temperature dependence in the region of 4.2-300 K.

Magnetic properties of Fe/EuO multilayered films

Abstract Iron (Fe) and europium monoxide (EuO) were multilayered by an ultra-high vacuum deposition method. X-ray diffraction and 151 Eu Mossbauer measurements have confirmed the formation of a single phase EuO. An anomalous temperature dependence of the magnetization suggests antiferromagnetic coupling at the interface and spin-glass-like behavior in the Fe layers.