Rhenium isotopes

In addition to Re and Re, 16 other radioactive rhenium isotopes ate known none has an appreciable half-life. 

Another type of ligand is the monoanionic, tridentate oxygen donor [(C5H4R)Co-(P(0)R R")3] (Lor), which has been used to prepare the complexes of technetium [37] and rhenium [38] [M03L] and [MOX2L] (X Cl, Br). These complexes are stable in organic solvents but hydrolyse slowly in water. In order to evaluate their usefulness in radioimmunotherapy, the corresponding compounds were also prepared with radioactive rhenium isotopes. 

Rheniums isotope ( Re) has a very long half-life and decays by both beta and alpha radiation at a very steady rate. This factor makes it useful as a standard to measure the age of the universe. 

For Re2(02CC Hs)4Cl2 the first reduction wave near —0.3 V is quasi-reversible. The product of this one-electron oxidation was not isolated as a solid, but ESR spectra were obtained on frozen dichloromethane solutions at 77°K at both X- and Q-band frequencies. Both naturally occurring rhenium isotopes have a nuclear spin of 5/2 with slightly different nuclear magnetic moments. For dimeric rhenium species there are three distinct isotopic isomers and each generates a unique ESR spectrum as a result of differing hyperfine interactions. The observed ESR spectrum is a superposition of these lines with the intensity... 

We think that the H,D replacement method is the method of choice to get an accurate determination of the dipolar term in the hydride moiety, as the overall T, of the hydride resonances may receive relevant contributions also from other relaxation sources. For instance, Beringhelli et al. showed that in (p-H)2Re2(CO)g the dipolar H—H relaxation accounts for only the 9.5 % of the total relaxation rate.[21] In this derivative the importance of the dipolar interactions with the metal itself is remarkable. In the case of Re i = 5/2 natural abundance = 37.07 % Re I = 5/2, natural abundance = 62.93 %) the small Y of rhenium isotopes is partially counterbalanced by the factor 1(1+1) = 8.75 which makes the effective 7 ca. 18 10 rad T s- (to be compared with 26.7223 10 rad T s- for H). In the extreme narrowing condition, for a hydride bound to it (r Re rhenium atom is as effective as an hydrogen atom... 

Natural rhenium is a mixture of two stable isotopes. Twenty six other unstable isotopes are recognized. 

Precise measurement of isotope ratios can be obtained by comparing the yields of isotopic ions desorbing from a sample placed on a strongly heated filament that is generally made from platinum, tantalum, rhenium, or tungsten. 

Since detailed chemical structure information is not usually required from isotope ratio measurements, it is possible to vaporize samples by simply pyrolyzing them. For this purpose, the sample can be placed on a tungsten, rhenium, or platinum wire and heated strongly in vacuum by passing an electric current through the wire. This is thermal or surface ionization (TI). Alternatively, a small electric furnace can be used when removal of solvent from a dilute solution is desirable before vaporization of residual solute. Again, a wide variety of mass analyzers can be used to measure m/z values of atomic ions and their relative abundances. 

Rhenium, atomic wt 186.2, occurs in nature as two nucHdes Re [14391-28-7] mass 184.9530, in 37.500% abundance and Re [14391-29-8], mass 186.9560, in 62.500% abundance. The latter isotope is radioactive, emitting very low energy radiation and having a half-life estimated at 4.3 ( 0.5) X 10 ° yr. The radioactive decay of this isotope has been used to date accurately the time of Earth s formation. 

The better known rhenium(V) chemistry is of great interest, not only because it resembles the second-row congener technetium and easily permits non-radio-active model studies for technetium. 186Re and 188Re are attractive isotopes for therapeutic radiopharmaceuticals. 99mTc and 186Re can be considered to be a matched pair for diagnostics and therapy. 

Iodine-131 was among the first radioactive isotopes used for radioimmunoconjugate preparation (Order, 1982 Regoeczi, 1984). Since the earliest studies on the efficacy of radiotherapy, additional isotopes have been employed, such as iodine-125, bismuth-212, yttrium-90, yttrium-88, technetium-99 m, copper-67, rhenium-188, rhenium-186, galium-66, galium-67, indium-111, indium-114 m, indium-115, and boron-10. 

Personnel working in some programs at the Los Alamos National Laboratory (LANL) may handle radioactive materials that, under certain circumstances, could be taken into the body. Employees are monitored for such intakes through a series of routine and special bioassay measurements. One such measurement involves a thermal ionization mass spectrometer. In this technique, the metals in a sample are electroplated onto a rhenium filament. This filament is inserted into the ion source of the mass spectrometer and a current is passed through it. The ions of the plutonium isotopes are thus formed and then accelerated through the magnetic held. The number of ions of each isotope are counted and the amount of Pu-239 in the original sample calculated by comparison to a standard. 

TEA chloride See tetraethylammonium chloride., te,e a klorjd ) technetium chem A transition element, symbol Tc, atomic number 43 derived from uranium and plutonium fission products chemically similar to rhenium and manganese isotope Tc has a half-life of 200,000 years used to absorb slow neutrons in reactor technology. tek ne-she-om ... 

ISOTOPES There are 45 isotopes of rhenium. Only one of these is stable Re-185, which contributes 37.40% to the total amount of rhenium found on Earth. Re-187, which is radioactive with a very long half-life of 4.35x10+ ° years, contributes 62.60% to rhenium s existence on Earth. The remaining 43 isotopes are radioactive with relatively short... 

Figure 11.28 shows the rhenium and osmium isotopic compositions of black shales and sulfide ores from the Yukon Territory (Horan et al., 1994). The black shale and sulfide layers are approximately isochronous. The superimposed reference isochrons bracket the depositional age of the enclosing shales. One reference line represents the minimum age (367 Ma) with an initial ( Os/ Os)q ratio of one, consistent with the mantle isotopic composition at that age (see later). The other reference isochron is drawn for a maximum age of 380 Ma, with ( 870s/ 860s)o = 12 (the maximum value measured in terrigenous sediments). Further examples of application of Re-Os dating of sediments can be found in Ravizza and Turekian (1989). 

Horan M. E, Morgan J. W, Grauch R. I., Coveney R. M. Jr., Murowchick J. B., and Hulbert L. J. (1994). Rhenium and osmium isotopes in black shales and Ni-Mo-PGE-rich sulfide layers, Yukon Territory, Canada, and Hunan and Guizhou provinces, China. Geochim. Cosmochim. Acta, 58 257-265. 

Riley, G.H. 1967. Rhenium concentration in Australian molybdenites by stable isotope dilution. Geochimica et Cosmochimica Acta, 31, 1489-1497. 

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