Yoichi Sakai

Bimetallic promotion of alcohol production in CO hydrogenation and olefin hydroformylation on RhFe, PtFe, PdFe, and IrFe cluster-derived catalysts

Iron-containing bimetallic catalysts were prepared from carbonyl clusters as precursors deposited on SiO2. FeRh4 and Fe2Rh4 cluster-derived catalysts showed high activity and selectivity for formation of ethanol and methanol in CO hydrogenation. Fe3Pt3, Fe6Pd6 and FeIr4 cluster catalysts gave methanol in high selectivity, while Fe-rich Fe4Pt and Fe4Pd were not selective catalysts. The RhFe cluster catalysts showed improved activity in hydroformylation of olefins; C4-alcohols were substantially obtained from C3 + CO + H2. Mossbauer and EXAFS studies on the Fe2Rh4/SiO2 catalyst show that highly dispersed RhFe bimetallic particles are located on the SiO2 surface, where Fe atoms exist preferentially in the state of Fe3+ even after H2 reduction. FTIR spectra of CO chemisorbed on Fe2Rh4/SiO2 exhibit a low-frequency band possibly due to the G and O-bonded CO on Rh-Fe3+ sites. Bimetallic promotion of alcohol production in CO hydrogenation and olefin hydroformylation is proposed to originate from the two-site interaction of Rh-Fe3+ (or Pt-Fe3+, Pd-Fe3+, IrFe3+) sites with CO to enhance migratory CO insertion.

[Fe4] and [Fe6] Hydride Clusters Supported by Phosphines: Synthesis, Characterization, and Application in N2 Reduction

Multiple iron atoms bridged by hydrides is a common structural feature of the active species that have been postulated in the biological and industrial reduction of N2. In this study, the reactions of an Fe(II) amide complex with pinacolborane in the presence/absence of phosphines afforded a series of hydride-supported [Fe4] and [Fe6] clusters Fe4(μ-H)4(μ3-H)2{N(SiMe3)2}2(PR3)4 (PR3 = PMe3 (2a), PMe2Ph (2b), PEt3 (2c)), Fe6(μ-H)10(μ3-H)2(PMe3)10 (3), and (η6-C7H8)Fe4(μ-H)2{μ-N(SiMe3)2}2{N(SiMe3)2}2 (4), which were characterized crystallographically and spectroscopically. Under ambient conditions, these clusters catalyzed the silylation of N2 to furnish up to 160 ± 13 equiv of N(SiMe3)3 per 2c (40 equiv per Fe atom) and 183 ± 18 equiv per 3 (31 equiv per Fe atom). With regard to the generation of the reactive species, dissociation of phosphine and hydride ligands from the [Fe4] and [Fe6] clusters was indicated, based on the results of the mass spectrometric analysis on the [Fe6] cluster, as well as the formation of a diphenylsilane adduct of the [Fe4] cluster.

Long-lived muonium in water revealed by pulsed muons

Abstract The relaxation rate of muonium in pure water has been found to be smaller than 0.05 × 10 6 s −1 . With the aid of pulsed muong. μSR and MuSR measurements have been carried out over a longer time range than ever achieved. The results indicate a stability of thermal muonium in water from 3 to 29°C.

Mössbauer spectroscopic study of phthalocyanineiron/II/ in NaY zeolite

Phthalocyanineiron/II/ in NaY zeolite was synthesized via various processes from an iron carbonyl compound into NaY zeolite in gaseous phase. Mössbauer spectra of the final product /phthalocyanineiron/II// and the precursor species /iron oxide and [phthalocyaninato/2-/]bis/pyridine/iron/II// in NaY zeolite were measured to characterize the chemical and physical states of the iron species.

Mössbauer spectroscopic study of the magnetic relaxation in tris(β-diketonato)iron(III) complexes

Abstract Mossbauer spectra of eleven kinds of tris (β-diketonato)iron(III) complexes were measured in order to investigate the magnetic relaxation effects. A correlation was observed between the Mossbauer line shape (linewidth) and the average iron-iron distance in crystals, mainly arising from the spin-spin relaxation. The dependency of line shape on temperature was also studied to check the contribution of the spin-lattice interaction.

Ejection of energetic7*Li ions produced in10B(n, α)7*Li reaction from boron coated silicon wafer

The spectral lines of the 478 keV prompt γ-ray from7*Li produced in the10B(n, α)7*Li reaction were measured for a silicon wafer coated with a thin boron layer using neutron beams. The shapes of the Doppler broadened lines were found to depend greatly on the angle between the measurement axis and the boron layer surface. The angular dependence was interpreted according to whether the energetic7*Li ions are ejected into air or into the substance in the forward or backward recoil of7*Li to the γ-ray detector.

Diamagnetic muon yields of metal acetylacetonates

Diamagnetic muon yields /PD/ in various metal acetylacetonates were measured at room temperature by the muon spin rotation technique. We have found a clear difference in PD between complexes of typical elements and those of transition elements. We suggest that partially filled inner orbitals play some important role in determining the diamagnetic yield in these complexes.

A μSR study on chemical behaviors of positive muons in crystalline tris/acetylacetonato/metal/III/ complexes

Chemical behaviours of positive muons implanted in crystalline tris/acetylacetonato/chromium/III/, iron/III/, and cobalt/III/ were investigated by means of the muon spin relaxation technique. The muon spin relaxation function was exponential in tris/acetylacetonato/iron/III/ and Gaussian in tris/acetylacetonato/cobalt/III/, suggesting that the muon spin relaxation may be ascribed to the interaction between the muon spin and a fluctuating electronic spin in the former and between the muon and a static nuclear spin in the latter. The yield of diamagnetic muon species was found to be nearly unity in these three complexes. Based on the analysis of the relaxation function, it is likely that the positive muon implanted in the cobalt/III/ complex will reside at a distance of about 1.7 A from the cobalt atom.

Distribution of boron in wood treated with aqueous and methanolic boric acid solutions

The distributions of boron in Japanese cedar (Cryptomeria japonica D. Don) sapwood blocks treated with aqueous or methanolic boric acid [B(OH)3] solutions were explored through Raman spectroscopy and prompt gamma-ray analysis (PGA). B(OH)3 was the sole boron species observed in Raman spectra of the wood blocks treated with either solution. Plots of weight gain of the treated wood blocks versus boron concentration in treatment solutions were found to be linear. The results indicated that the methanolic solution makes it possible to impregnate wood with much larger amounts of boron than the aqueous solution. PGA confirmed that B(OH)3 was highly enriched near the end grains of the treated wood blocks. Raman measurements suggested that boron content in the bulk of the wood block is not as large as expected from the weight gain of the treated wood blocks when an ordinary air-drying method is used. It was concluded that the aqueous solution impregnates the cell walls of wood with boron more easily than the methanolic solution.

Mössbauer characterization and prompt gamma-ray analysis of the products of thermit reactions

Iron and boron species in the products of thermit reaction of aluminum, iron oxide, and boron oxide were characterized by Mössbauer spectroscopy, X-ray diffraction, and prompt γ-ray analysis. It was revealed that iron and boron products of the thermit reaction are composed of intermetallic compounds with aluminum.