[en] The authors recently reported that anions, in particular isocyanate, were effective in converting normally unreactive Ru₃(CO)₁₂ into an active catalyst (5-6 turnovers/min under ambient conditions) for alkene hydrogenation. While both spectroscopic and kinetic evidence supported a catalytic cycle involving an intact ruthenium triangle, no intermediates were isolated. With the hope of isolating such species, they turned to the osmium system and have found a rich chemistry that is reported here. The authors initially synthesized the anionic osmium isocyanato clusters using the same reaction found successful in the ruthenium chemistry. The osmium cluster chemistry presented here provides evidence for the intermediates proposed. While less active than the ruthenium system, these isocyanate-promoted osmium clusters also catalyze the hydrogenation of olefins

[en] The synthesis of tert-butylarsine-d₂ from tert-butylarsenic dichloride and LiAlD₄ is described. No resonances at 2.65 ppm (from AsH₂) are observed in the ¹H NMR spectrum, indicating the isotopic purity is greater than 95%. The pyrolyses of tert-butylarsine and tert-butylarsine-d₂ were studied by using a flow reactor operated between 425 and 550 degree C at total pressures of 0.001, 5, and 700 Torr. At 5 and 700 Torr, nitrogen was used as the carrier gas. The volatile products of the reaction were trapped in a liquid nitrogen cooled trap, transferred under vacuum into an NMR tube, and quantitatively analyzed by using ¹H NMR spectroscopy. Three important results from the study are (1) the isobutane produced during the pyrolysis of tert-butylarsine-d₂ was Me₃CD, (2) C₂Me₆ was proven not to be a product of the reaction, (3) isobutane was found to be the major product at atmospheric pressure, while isobutene was predominant at low pressures in agreement with previous studies

[en] A comparison of the use of three different coordination compounds of copper as precursors for the sol-gel synthesis of YBa₂Cu₃O_7-δ is presented. For yttrium, the tris (isopropoxide) was used exclusively, while the use of both Ba(O-i-Pr)₂ and Ba(OCH₂CH₂OEt)₂ (prepared in situ from Ba metal) as sources for Ba were studied. After dissolving Y(O-i-Pr)₃, a Ba source, and the copper(I) alkoxide, [Cu(O-t-Bu)]₄, hydrolysis led immediately to an orange gelatinous solid which yielded YBa₂Cu₃O_7-δ upon firing in oxygen. Copper (II) acetate was found to give heterogeneous mixtures under our conditions and was not further studied. Copper (II) acac (acac = acetylacetonate) yielded the best results. Partially hydrolyzed solutions of Cu(acac)₂, Ba(OCH₂CH₂OEt)₂, and Y(O-i-Pr)₃ were spin coated on SrTiO₃ (100) and fired under oxygen to give oriented (b axis normal to the surface) thin films of YBa₂Cu₃O_7-δ. The onset of superconductivity for the films was 92 K, but they did not reach zero resistance until much lower temperatures

[en] A low-pressure CVD reactor was modified to create continuous compositional spreads of ZrO₂/HfO₂/SnO₂ on a single Si(100) wafer. Anhydrous metal nitrates were used as single-source precursors to grow the films, and the compositions were mapped using Rutherford backscattering spectroscopy (RBS). An array of 100 x 100 μm² capacitors was used to map the dielectric constant. High dielectric constants were observed for the films having high ZrO₂ concentrations, while high SnO₂ concentrations correlated with low values of κ. (Abstract Copyright [2004], Wiley Periodicals, Inc.)

[en] A quantitative study was made of the composition and microstructure of RuO₂ films deposited on three different substrates using reactive sputtering. Most of the films had a composition within 2.5 wt.% of the correct stoichiometry; the only exceptions were films grown on Al₂O₃(0001) at 150 degree C, which had an oxygen-to-ruthenium ratio of 1:2.24. The excess oxygen was attributed to a thin oxygen-rich layer that encapsulated the grains. Hydrogen concentrations for the films deposited on Al₂O₃(0001) were 14, 6, 6, and <0.5 at.% for room, 150, 300, and 450 degree C growth temperatures respectively. The films deposited at room temperature were amorphous on Al₂O₃(0001) and SrTiO₃(100), but weakly crystalline on Al₂O₃(1 bar 102). Highly oriented RuO₂(100) films were produced on Al₂O₃(0001) at deposition temperatures ≥150 degree C. The in-plane alignment was [010]_RuO2//left-angle bar 2110 right-angle _Al2O3 and a threefold mosaic microstructure was observed. The grain boundaries in these films were discontinuous until the substrate temperature was raised to 450 degree C, where coherent grain boundaries were formed. The films grown on Al₂O₃(1 bar 102) at 450 degree C exhibited the epitaxial relationship: RuO₂(101)//Al₂O₃(1 bar 102). The in-plane alignment was RuO₂ left-angle 101 right-angle//Al₂O₃ left-angle bar 1101 right-angle, and the lattice parameters were the same as found in bulk RuO₂. Transmission electron microscopy indicated a large degree of imperfection in the region between coalescing grains. The RuO₂ films grown on SrTiO₃(100) at room temperature were amorphous. The film grown at 450 degree C showed a preferential orientation with RuO₂(100)//SrTiO₃(100), but without in-plane orientation. copyright 1997 Materials Research Society