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  • Author or Editor: M. Takeda x
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Abstract  

121Sb Mössbauer spectra of the title complexes, whose isomer shifts are intermediate between the organoantimony(III) and organoantimony(V) compounds, suggest that considerable electrons are donated from hydrido ligand and Fe(CO)4 fragments to the antimony atom.

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Abstract  

An analytical scheme of radiochemical neutron activation for the sequential determination of ultra-trace rare earth elements (REEs) and highly siderophile elements (HSEs) in geological and cosmochemical samples is presented. Using this procedure, several selected elements of REEs and HSEs were successively determined for geological reference samples and olivine crystals separated from pallasite meteorites. Based on the data for geological reference samples, it was concluded that the procedure presented in this study could yield data usable for cosmochemical discussion of the genesis of pallasite meteorites.

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Abstract  

A simple and effective radiochemical procedure for radiochemical neutron activation analysis (RNAA) of ultra-trace siderophile elements (Ru, Re, Os and Ir) and rare earth elements (REEs) in rock and meteorite samples is presented. To design the procedure, several separation schemes of siderophile elements were examined by using radioactive tracers. By applying the procedure to rock and meteorite samples, we have determined Ru, Re, Os, Ir and REEs, and confirmed that our values were in agreement with the literature values. Our detection limits for Ru, Re, Os, La, Sm and Eu are significantly low compared with those for ICP-MS.

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Abstract  

121Sb Mössbauer spectra for M3Sb (M3 = Na3, K3, Na2K, Rb3) were measured at 12 K. The values of isomer shift (d) and quadrupole coupling constant suggest that the valence state of antimony in M3Sb is –3. The d values increase in the order Rb3Sb<K3Sb<Na3Sb<Na2KSb. The differences in d values are discussed by examining M–Sb distances and bond valence for M–Sb interactions. Some covalent interactions between alkali metal atoms and antimony atom are suggested.

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Abstract  

127I Mössbauer spectra for the phenyliodonium ylides were measured at 20 K. The valence electron populations (Ns, Nx-z) and the charge number (ZI) for iodine atom are estimated from the Mössbauer parameters. The obtained populations were very close to those of diphenyliodonium chloride having two I-C primary bonds. To examine the possibility of some double bond character, the electron populations for the case of Nz = 1.90 are estimated. In this case, the ZI values become larger as 1.2-1.3, and these values were unreasonably large because the values are close to those of PhICl2, PhI(OAc)2 having electron withdrawing ligands. Thereby, 127I Mössbauer parameters suggest little double bond character for phenyliodonium ylides.

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Abstract  

155Gd Mössbauer spectra of some Gd(III)-b-diketonato complexes are reported. All of their 155Gd Mössbauer isomer shift (d) values fall in a narrow range of +0.55-+0.65 mm.s-1, and are between those of GdF3 and the cubic form of Gd2O3. This indicates that their Gd-O bonds have small covalent character. The value for quadrupole coupling constant (e2qQ) spread out from 1.67 to 7.56 mm.s-1 and reflects the difference well in symmetry of the coordination polyhedron around Gd(III) ions for those Gd(III)-b-diketonato complexes.

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Abstract  

We have compared the 127I Mössbauer spectra of eleven organoantimony compounds with hypervalent bonding, E-Sb-I (E = O, I, N, C ). The charges on iodine atoms fall between -0.54 e for the compound with Sb-I bond length of 2.83 Å and -0.82 e for the compound with 3.34 Å. The negative charges on iodine atoms have been found to increase with the increase in the Sb-I bond lengths. Regarding to the dependence of the kind of E atoms, the negative charges on iodine atoms have been found to decrease with the increase in the electronegativities of E atoms. 121Sb Mössbauer spectra have shown the decrease of the group oxygen electronegativity of hexafluorocumyl alcohol by substituting CF3 for CH3, and this was reflected through O-Sb-I bonding as the increase in the negative charges of iodine atoms in the 127I Mössbauer spectra.

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Abstract  

Four kinds of Dy(III) hexacyanometalates (II or III), DyFe(CN)6·4H2O (1), KDyFe(CN)6·4H2O (2), DyCo(CN)6·4H2O (3), and KDyRu(CN)6·4H2O (4) have been investigated by 161Dy Mössbauer spectroscopy. 161Dy isomer shifts of four compounds fall in the range of +3 ionic compounds. Although all spectra 1-4 show an almost symmetric line, the broadening of the line-width is observed on lowering the temperature due to the paramagnetic relaxation. As a parameter of intermolecular force constant, the M 2 value obtained for 161Dy of 1 is slightly larger than that of 2.

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Summary  

The correlations of isomer shifts in various neptunyl(V and VI) compounds with crystallographic structures were revaluated. A linear correlation between the isomer shifts of neptunyl(VI) compounds and Np-O bond lengths of neptunyl group has been demonstrated. On the other hand, it has been evidenced that the isomer shifts of neptunyl(V) compounds are correlated much stronger with the mean Np-O distances in the crystals than the lengths in neptunyl(V) group.

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Abstract  

The coordination polymer Fe(3-chloropyridine)2Ni(CN)4 (2) has been prepared by a method similar to that for Fe(pyridine)2Ni(CN)4 (1). The complex (2) has been characterized by57Fe Mössbauer spectroscopy and a SQUID technique.57Fe Mössbauer and magnetic susceptibility data show that complex (2) exhibits spin-crossover behavior. The spin transition of (2) occurs between 120 and 80 K with very small hysteresis or without hysteresis. The temperature range of the spin transition in (2) is lower than that in (1). A residual high spin iron(II) fraction is observed at low temperatures in (2), being different from (1). SQUID data also show that samples treated differently yield different spin transition curves.

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