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.
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.
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.
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.
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.
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.
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.
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.
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.
We have measured the 57Fe Mössbauer spectra of the Hofmann pyridine complex Fe(pyridine)2Ni(CN)4 sample before and after exposure to high pressure of gaseous xenon. The temperature dependence of the high spin molar fraction has been determined from the 57Fe Mössbauer spectra. The spin transition of the sample without the high pressure treatment occurs between 175 and 220 K with a hysteresis width of 15 K. Although the 57Fe Mössbauer spectra suggest that the spin crossover behavior of the sample before and after the high pressure treatment are almost the same, the hysteresis of the latter sample is somewhat larger.