Copolymerization of ethylene with cycloolefins or cyclodiolefins by a constrained‐geometry catalyst

The copolymerization of ethylene and cycloolefins [cyclopentene (CPE), cyclohexene (CHX), cycloheptene (CHP), cyclooctene (COT), cyclododecene (CDO), norbornene (NB), and 5,6‐dihydrodicyclopentadiene HDCPD] and cyclodiolefins [1,3‐cyclopentadiene (CPD), 1,4‐cyclohexadiene (CHD), 1,5‐cyclooctadiene (COD), 2,5‐norbornadiene (NBD), and dicyclopentadiene (DCPD)] was investigated with a constrained‐geometry catalyst, dimethylsilylene(tetramethylcyclopentadienyl)(N‐tert‐butyl)titanium dichloride, with methyl isobutyl aluminoxane as a cocatalyst. In the copolymerization with cycloolefins, the olefins, except for CHX, CDO, and HDCPD, were copolymerized via the 1,2‐insertion mode with the following reactivity: NB > CHP > COT > CPE. In the copolymerization with cyclodiolefins, corresponding copolymers, except for copolymerization with CHD, were obtained. A crosslinking fraction was detected in the copolymers with COD and NBD. The reactivity of the cyclodiolefins, except for COD, was higher than that of the cycloolefins. CPD was copolymerized via 1,2‐insertion, 1,4‐insertion or 1,2‐insertion of dimerized DCPD. The copolymerization with COD showed peculiar behavior under the copolymerization condition of a high COD concentration in the feed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1285–1291, 2005     

Effect of supports on copper Catalysts for Methanol Synthesis from CO2 + H2

Methanol was synthesized from carbon dioxide and hydrogen over various supported copper catalysts. A support was selected from the viewpoint of its acid-base properties. Acid supports showed high selectivity but low activity. Neutral and basic supports produced only carbon monoxide. Amphoteric supports showed high activities. Among them, TiO₂ supports suppressed the reverse water gas shift reaction (CO formation). The role of supports was discussed on the basis of in situ infrared results.     

X-ray photoelectron spectroscopic study on initial oxidation of hafnium hydride fractured in an ultra-high vacuum

The initial oxidation of hafnium hydride was studied by X-ray photoelectron spectroscopy (XPS). The clean surface of hafnium hydride was obtained by fracturing the specimen in an XPS measurement chamber under a background pressure of 2.7 × 10⁻⁶ Pa. The fractured surface was oxidized in situ with the exposure to high-purity oxygen and the residual gases in an ultra-high vacuum chamber. The XPS spectra for the oxidized surfaces had the shoulder due to the oxidation, and the shoulder grew up with increase in exposure time even in the ultra-high vacuum. The factor analysis for the XPS spectra of the oxidized surface showed that the oxide formed in the chamber consists of only the hafnium dioxide, and no suboxide states are contained. The result corresponded to the oxide observed on hafnium hydride fractured in air.     

X-ray photoelectron spectroscopic studies on phase identification and quantification of nickel aluminides

Core-level XPS spectra for clean surfaces of Ni₃Al, NiAl, and NiAl₃ alloys were studied. The clean surfaces were obtained by fracturing in the ultra-high vacuum chamber. The positive chemical shifts of Ni 2p_3/2 peak for NiAl and NiAl₃ from Ni metal were 0.2 and 1.0 eV, respectively. The negative shift for Al 2p peak and the positive shift for Ni 3p peaks increased with the decreasing concentration of the corresponding elements. The peak position of the bulk plasmon loss peak for Al 2s peak shifted toward higher energy side, and further, the intensity ratio decreased with the decrease in aluminum concentration. Both the peak intensity ratios of Al 2p to Ni 3p determined by factor analysis and convenient separation are proportional to the atomic ratio of aluminum to nickel. The results indicate that the intensity ratio of Al 2p to Ni 3p determined by these two methods can be applied to the quantification for the surface of the nickel-aluminum alloys.     

Palladium-catalyzed benzannulation from alkynes and allylic compounds

Various alkynes reacted with allyl tosylates in the presence of palladium catalysts, giving polysubstituted benzenes with good to high regioselectivity. Pentasubstituted and trisubstituted benzenes were readily prepared by reaction of internal alkynes and terminal alkynes, respectively. The combination of allyl alcohols and p-toluenesulfonic anhydride could be utilized in place of isolated allyl tosylates. The cyclization of diynes with allyl tosylate afforded bicyclic compounds containing an aromatic ring.     

Effect of acid-base properties on copper catalysts for hydrogenation of carbon dioxide

Acidic or basic components as co-catalysts were added to the Cu-based catalysts for hydrogenation of CO₂. Effects of acid-base properties on the catalytic activity and methanol selectivity are discussed.     

Integrated Micro Flow Synthesis Based on Sequential Br–Li Exchange Reactions of p‐, m‐, and o‐Dibromobenzenes

A micro flow system consisting of micromixers and microtube reactors provides an effective method for the introduction of two electrophiles onto p‐, m‐, and o‐dibromobenzenes. The Br–Li exchange reaction of p‐dibromobenzene with nBuLi can be conducted by using the micro flow system at 20 °C, although much lower temperatures (p‐bromophenyllithium was allowed to react with an electrophile in the micro flow system at 20 °C. The p‐substituted bromobenzene thus obtained was subjected to a second Br–Li exchange reaction followed by reaction with a second electrophile at 20 °C in one flow. A similar transformation can be carried out with m‐dibromobenzene by using the micro flow system. However, the Br–Li exchange reaction of o‐dibromobenzene followed by reaction with an electrophile should be conducted at ?78 °C to avoid benzyne formation. The second Br–Li exchange reaction followed by reaction with an electrophile can be carried out at 0 °C. By using the present method, a variety of p‐, m‐, and o‐disubstituted benzenes were synthesized in one flow at much higher temperatures than are required for conventional batch reactions.     

Comparison of intrinsic zero-energy loss and Shirley-type background corrected profiles of XPS spectra for quantitative surface analysis: Study of Cr, Mn and Fe oxides

The intrinsic zero-energy loss profiles of transition metal 2p and 3p XPS spectra for Cr, Mn, and Fe oxides are obtained by spectral deconvolution and compared with Shirley-type background corrected profiles. The metal core level spectra are deconvoluted by O 1s spectra as the response function of each oxide. As the O 1s spectra include intrinsic and extrinsic energy loss parts, the background corrected core level spectra are zero-energy loss spectra. The good agreement of the deconvoluted spectra with the reported spectra obtained by the many body effect theory indicates that the background subtraction method is accurate. A comparison of the deconvoluted with the background corrected spectra of the Shirely-type subtraction reveals that almost all the spectra coincide with each other except for Fe 3p with -Fe₂O₃. The good coincidence of the Shirley-type corrected spectra with the deconvoluted and calculated spectra indicates that Shirley-type background correction can be used for daily quantitative surface analysis.     

Ab initio conformational analysis of 1,5‐dithiacyclooctane, 1,5‐diselenacyclooctane,and 1,5‐ditelluracyclooctane

Energy‐minimum structures of 1,5‐dithiacyclooctane (1,5‐DTCO), 1,5‐diselenacyclooctane (1,5‐DSeCO), and 1,5‐ditelluracyclooctane (1,5‐DTeCO) were calculated by the ab initio molecular orbital method. Nine energy‐minimum structures were obtained for each compound. A twist‐boat–chair (TBC) structure is the most stable for 1,5‐DTCO and 1,5‐DSeCO, whereas a boat–boat (BB) structure is the most stable in 1,5‐DTeCO. The TBC conformer of 1,5‐DTCO has received little attention so far. The energy gap between HOMO and NHOMO in the TBC conformer of 1,5‐DTCO is in good agreement with the experimental data (photoelectron spectrum). For 1,5‐DTCO and 1,5‐DSeCO, the boat–chair (BC) conformer in which two chalcogen atoms face each other has the highest HOMO energy among the nine conformers, and the energy barriers between the TBC and BC conformers were calculated to be relatively low for these compounds. Therefore, a conformational change from the TBC to the BC is predicted to occur before these compounds are oxidized in solution. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 159–166, 1999