Rhenium homologs

Other than (CO)4Fe(CHO) and derivatives thereof (22-25), only a few of the formyl complexes in Table I show significant stability at room temperature. Of these, the binuclear rhenium formyl cis-(CO)5ReRe(CO)4(CHO) [19, Eq. (5)] has received the greatest attention (37. 38. 42. 47). The manganese and mixed manganese/rhenium homologs (12, 18) can be similarly prepared, but are less stable (35. 38, 47). 

An alternative route to the mononuclear dinitrogen complex is by the reaction of [(ij5-CsH5)Mn(CO)2(N2Ari r and its rhenium homologs with nucleophiles such as Cl, Br, I, Cn, and SCN. This has poten-... 

Rhenium chemistry will not be discussed explicitly in this contribution. Various excellent reviews on the progress of organometallic rhenium chemistry have been published over recent years. [7] Rhenium is only mentioned when its comparison to new technetium compounds is interesting in the present context and the focus is on significant differences in the behaviour of the two homologs. 

Thiourea complexes of technetium(III) have been shown to be excellent precursors for the synthesis of a large number of Tc and Tc complexes. The [Tc(tu)6] cation is readily formed in a mixture of pertechnetate, tu and 12 M HCl and precipitates as chloride. Due to the different redox potentials of the homologous elements technetium and rhenium, the reducing capacity of HCl is not sufficient to apply the same method for rhenium and tin chloride is added as reducing... 

In contrast to the chalcogen-bridged complexes, no similar oxygen-bridged compounds of iron, cobalt, or nickel exist. However, we obtained such oxo or i-ol-carbonyl complexes of chromium and its homologs, as well as of rhenium. The compounds are the products of the reactions of the respective metal carbonyls with bases (VII). 

Progress in technetium chemistry obviously depends on sensitive analytical methods to detect this radioelemcnt, to efficiently separate it, and to determine technetium accurately. Several reviews on the analytical chemistry of technetium have been published [1-7]. Even the discovery of technetium was conclusive only because separation techniques known at the time for the homologous element rhenium were used 8. Furthermore, the detection of naturally occurring technetium or the determination of the element in the environment presupposed the application of highly sensitive methods. The effective extraction of pcrtechnctate into organic solvents for the isolation of technetium from fission product waste solutions is. in addition, an example of the significance of appropriate techniques in analytical chemistry. 

Nonisotopic carriers can be used when no isotopic carrier exists. Rhenium is a carrier for technetium, lanthanum for promethium and plutonium, and barium for radium. Such chemical homologs do not have identical solubility products, hence their yields may differ and must be compared by testing. Group separations can be... 

This reaction has been in contrast successfully applied for the synthesis of alkoxide derivatives of acidic oxides, as the whole homologous series of vanadium alkoxides (Orlov, 1959 Prandtl, 1913), and for the preparation of a number of hydrocarbon soluble complexes with diols ofmolybdenum(Vl) (Bishop, 1979), rhenium(VI) (Edwards, 1998) and... 

Chemical identification is a desirable method for detection of a new element Chemical identification of the elements immediately beyond hahnium (element 105) should be possible, but rapid chemical reactions will be required. Chemical properties can be predicted with the help of the periodic table shown in Fig. 24.1, which indicates that elements 106,107, 108, etc., should be chemical homologs, respectively, of tungsten (W), rhenium (Re), osmium (Os), etc. The utilization of volatility properties perhaps offers the best possibility for very rapid chemical identification. The hexafluoride and hexacarbonyl of element 106 (eka-tungsten) should be quite volatile and the hexachloride, pentachloride, and oxychlorides... 

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