Ruthenium isotope

Synthesis of ruthenocene from fission-product ruthenium isotopes was done by neutron irradiation ofU30g and FeCpj powder mixtures. It was shown that most of the ruthenocene found was actually produced by the decay of a precursor. Subsequent knowledge makes it apparent that the fission product recoils formed a rhodium dicyclopentadienide whose structure was preserved through the decay . The total yield of ruthenocene reached a value of 60% under some experimental conditions and was rarely less than 40%. 

Potzel et al. [Ill] have established recoil-free nuclear resonance in another ruthenium nuclide, ° Ru. This isotope, however, is much less profitable than Ru for ruthenium chemistry because of the very small resonance effect as a consequence of the high transition energy (127.2 keV) and the much broader line width (about 30 times broader than the Ru line). The relevant nuclear properties of both ruthenium isotopes are listed in Table 7.1 (end of the book). The decay... 

Short-lived ruthenium Isotopes, such as 52-second Ru produced by a particle bombardment of molybdenum (10) and the... 

Upon collisional activation, these ions lose masses of 27 and 41, respectively, restoring the original propene complex. Mass selection of different ruthenium isotopes confirms these assignments. 1-Butene reacts with ruthenium... 

A typical SSIMS spectrum of an organic molecule adsorbed on a surface is that of thiophene on ruthenium at 95 K, shown in Eig. 3.14 (from the study of Cocco and Tatarchuk [3.28]). Exposure was 0.5 Langmuir only (i.e. 5 x 10 torr s = 37 Pa s), and the principal positive ion peaks are those from ruthenium, consisting of a series of seven isotopic peaks around 102 amu. Ruthenium-thiophene complex fragments are, however, found at ca. 186 and 160 amu each has the same complicated isotopic pattern, indicating that interaction between the metal and the thiophene occurred even at 95 K. In addition, thiophene and protonated thiophene peaks are observed at 84 and 85 amu, respectively, with the implication that no dissociation of the thiophene had occurred. The smaller masses are those of hydrocarbon fragments of different chain length. 

The radiochemistry of ruthenocene has been studied by Baumgartner and Reichold (9) and by Harbottle and Zahn (29). It is found that neutron irradiation of crystalline RuCp2 yields about 10% of the radioactive ruthenium as RuCp2- More specifically, an isotopic difference in the radiochemical yield is found Ru, 9.6 0.1% Ru, 10.7 0.2% and Ru, 9.9 0.2% (29). In liquid solution the isotopic effect is much more pronounced, although the yields are lower. This was suggested by Harbottle as a general principle the greatest isotope effects are associated with the lowest yields. While this principle has not yet been substantiated, it seems reasonable since any thermal reactions which may increase the yields would not likely show any isotope effect. 

The exchange between the ruthenium anions RuO and RuO " in aqueous hydroxide media has been found rapid. A limit for the rate coefficient at 0 °C of > 1.7x10 l.mole . sec has been proposed by Luoma and Brubaker. The isotopic method ( ° Ru), and separation procedures based on the precipitation of the Ru04 or RuOJ species with barium or tetraphenylarsonium ions, respectively, were used. Attempts to use an esr technique failed. 

Silene-transition metal complexes were proposed by Pannell121 for some iron and tungsten systems, and such species were observed spectroscopically by Wrighton.122,123 Thus intermediates such as 33 have been proposed in the preparation of carbosilane polymers from hydrosilanes,124 both as intermediates in the isotope scrambling observed to occur in similar ruthenium hydride systems125 126 and in the 5N2 addition of alkyllithium species to chlorovinylsilanes.47... 

Das Technetium besitzt keine betastabilen Isotope, da die hierfiir in Frage kommenden Massenzahlen 97 und 99 durch betastabile Isobare der Nachbarelemente Molybdan und Ruthenium besetzt sind. 

Beim Bestrahlen von Ruthenium mit schnellen Neutronen sowie bei der Spaltung des Urans mit 28 MeV-Deuteronen 166), (171) wurde ein Tc-Isotop mit der Halbwertszeit 18 min beobachtet. (Qfj.= S MeV.) Es liegt vermutlich ein Kemisomeres von Tc 104 vor. 

The ruthenium-catalyzed isotope exchange of boron atoms in decaborane is remarkable because several bonds are selectively broken and formed with a nanoscale catalyst without altering the structure of the decaborane. Highly enriched [10B] decaborane can be obtained by repeated treatment (six times) of decaborane with 10B2H6 in presence of Ru(0) NPs in ILs (entry 3, Table 1.5 Scheme 1.5), where the catalyst was recycled three times in batch experiments without significant activity loss [107]. 

An interesting catalytic ruthenium system, Ru(7/5-C5Ar4OH)(CO)2H based on substituted cyclopentadienyl ligands was discovered by Shvo and coworkers [95— 98]. This operates in a similar fashion to the Noyori system of Scheme 3.12, but transfers hydride from the ruthenium and proton from the hydroxyl group on the ring in an outer-sphere hydrogenation mechanism. The source of hydrogen can be H2 or formic acid. Casey and coworkers have recently shown, on the basis of kinetic isotope effects, that the transfer of H+ and TT equivalents to the ketone for the Shvo system and the Noyori system (Scheme 3.12) is a concerted process [99, 100]. 

There is only one detailed kinetic study of ruthenium enantioselective hydrogenation, in this case involving (BINAP)Ru(OAc)2, and MAC [65]. The extensive study involved reaction kinetics, isotopic analysis of reaction components and products, and in-situ NMR. The derived catalytic cycle is shown in Figure 31.15, differing from the Bergens studies described above in that the intermediates -both observed and assumed - are neutral rather than cationic. Right up to the formation of the alkylruthenium intermediate, the individual steps are revers-... 

The most active Pd based catalysts in the table have been reported by Shishido et al.51 who have employed hydrotalcite precursors, using a solid phase crystallisation (SPC) method. Comparisons made with catalysts prepared via impregnation showed SPC to afford higher activity catalysts, which was ascribed to better dispersion and also easy desorption of CO. The inclusion of a Cr component in these types of catalyst has also been reported to be beneficial.52 In terms of the desorption of CO, isotopic studies performed by McKee53 over ruthenium and platinum catalysts have indicated that the rate determining step of methanol decomposition is the fission of a... 

Radiation activity levels for a dirty bomb made with spent fuel depend on the age of the fuel. A simple rule to consider is that any radionuclide will decay to 1% of the original concentration after seven half-lives or will decay to insignificant concentrations after ten half-lives. Therefore, if a fuel rod is removed from a reactor several days before detonation in a dirty bomb, all the isotopes listed in Table 2.1 will likely be present. If a fuel rod was last used in a reactor 5 years before detonating a bomb, ruthenium-106 and cerium-144 will have decayed to insignificant concentrations. 

The isotope effects for transfer of hydrogen were 1.79 for transfer from OH to N and 2.86 for transfer from CH to ruthenium. The isotope effect for transfer of the doubly labelled material d% 2-propanol) was 4.88, within the experimental error. If the hydrogen atoms would be transferred in separate... 

Hydrogen iodide in ruthenium catalysis, 32 397-400, 405 06 Hydrogen isotopes... 

Dr. Erickson For those interested in coordination chemistry, certain other transition metal atoms are suitable for Mossbauer spectroscopy. One in particular is ruthenium which is just below iron in the Periodic Table. It is a difficult isotope to work with since it requires helium temperatures almost exclusively. I don t know whether it is possible to work at nitrogen temperatures or not, but Kistner at Brookhaven has examined various ruthenium compounds from the 2-j- to the 8+ oxidation states with interesting results. These are not published yet, but at least his work offers the possibility of going down one element below the other in the Periodic Table to study chemical effects. Osmium, which is below ruthenium, can also be Mossbauered. Some sort of systematic study like this involving elements in the various transition series would be extremely interesting. 

Example Ruthenium exhibits a wide isotopic distribution where the ° Ru isotope can be used as a marker during assignment of mass differences. Moreover, the strong isotopic fingerprint of Ru makes it easily detectable from mass spectra and even compensates for a lack of information resulting from moderate mass accuracy (Fig. 3.10). 

Fig. 3.10. Calculated and experimental (FD-MS, cf. Chap. 8.5.4) isotopic pattern of a ruthenium carbonyl porphyrin complex. The isotopic pattern supports the presumed molecular composition. The label is attached to the peak corresponding to the ° Ru-contaming ion. Adapted fromRef. [17] with permission. IM Publications, 1997.

Example The FD spectrum of a ruthenium-carbonyl-porphyrin complex shows an isotopic pattern very close to the theoretical distribution (Chap. 3.2.8). The loss of the carbonyl ligand chiefly results from thermal decomposition. A spectmm accumulated close to BAT (scans 19-25, EHC = 25-30 mA) is nearly free from CO loss while a spectrum accumulated of scans 30-36 (35 0 mA)... 

Ruthenium is found in South America and the Ural Mountains of Russia. There are some minor platinum and ruthenium ores found in the western United States and Canada. All of the radioactive isotopes of ruthenium are produced in nuclear reactors. 

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