Rhenium complexes thiourea

Hi) Rhenium(V) complex with NCS (191), thiourea, and other incoming ligands (205). The observed linear free-energy relationship also suggests dissociative activation for the substitution reactions of the rhenium complex (205). 

Non-ionic thiourea derivatives have been used as ligands for metal complexes [63,64] as well as anionic thioureas and, in both cases, coordination in metal clusters has also been described [65,66]. Examples of mononuclear complexes of simple alkyl- or aryl-substituted thiourea monoanions, containing N,S-chelating ligands (Scheme 11), have been reported for rhodium(III) [67,68], iridium and many other transition metals, such as chromium(III), technetium(III), rhenium(V), aluminium, ruthenium, osmium, platinum [69] and palladium [70]. Many complexes with N,S-chelating monothioureas were prepared with two triphenylphosphines as substituents. 

A more efficient method of paper chromatography was developed by Beckman and Lederer making use of the formation of a technetiiun complex with thiourea in nitric acid. TcO is reduced by this reagent, in contrast to ReO". The paper is eluted with 2 N HCl. The R, values of technetium and rhenium have been found to be very different, namely 0.2 and 0.7, respectively. 

Re—O—Re linkage.The complexing of rhenium(iv) with thiourea (L) has been studied in HCl solutions in the presence of tin(ii) by a cation-exchange method, and equilibrium stability constants Pj—P4 for [ReOL4] -t- nCl" [ReOCl L4 -I- nh determined.The complexing of rhenium(iv) with thiocyanate ions in HCl solutions in the presence of SnClj has also been investigated and the formation of a 1 1 Re -SCN" complex confirmed. ° ... 

Early reports on the formation of thiourea rhenium(V) oxo complexes by simple reduction of [Re04] with HCl in the presence of thiourea (tu) could not be verified. A detailed study of this reaction clearly indicates that this reaction (as with other thiourea derivatives) yields the rhe-nium(III) complex [Re(tu)g] in excellent yields. Details will be discussed in Section 5.3.2.5.2(ii). However, a stable rhenium(V) oxo complex could be isolated with the bulky tetramethylthiourea (Me4tu). The red compound represents one of the rare examples of a triply positive charged rhenium(V) monoxo complex. Quantum chemical studies (semiempirical MNDO-PM3 level and... 

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... 

Rate laws and rate constants have been determined for the reactions of the dinuclear rhenium(ni) complexes [RcaXg] with thiourea or tris-n-butyl-phosphine in methanol. The kinetic pattern suggests the reaction sequence shown in Scheme 3. The reaction of [Re2Brg] - with chloride ion was also studied. ... 

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