Technetium and Rhenium

Three-Fold Intramolecular Ring Closing Alkene Metatheses of Square Planar Complexes with cis Phosphorus Donor Ligands P(X(CH2)mCH═CH2)3 (X = −, m = 5–10; X = O, m = 3–5): Syntheses, Structures, and Thermal Properties of Macrocyclic Dibridgehead Diphosphorus Complexes

“…Data for the four types of isomeric rhenium complexes in Scheme are provided in Figure . Consistent with the thermolyses in Scheme , and the direction of equilibrium for a number of related complexes, mer , trans - 12′c and mer , trans - 13′c were found to be much more stable than fac - 12′c and fac - 13′c (−5.4 to −7.4 kcal/mol). Interestingly, the energies of the previously synthesized gyroscope-like complexes mer , trans - 12c and mer , trans - 13c were quite close to those of the parachute-like complexes fac - 12c and fac - 13c (≤0.4 kcal/mol).…”

“…As shown in Scheme , the thermolysis of fac - 11c in C 6 H 5 Cl at 140 °C afforded the previously characterized isomer mer,trans - 11c in 89% yield. Many earlier studies have shown that mer , trans isomers of rhenium tricarbonyl bis­(phosphine) halide complexes are more stable than fac isomers . As noted previously, when mer , trans - 11c is subjected to the standard metathesis/hydrogenation conditions, the corresponding gyroscope-like complex mer , trans -ReBr­(CO) 3 (P­((CH 2 ) 14 ) 3 P) ( mer , trans - 12c ; Scheme ) can be isolated in 37% yield. …”

A Convenient Three-Component Synthesis of Substituted Cyclopentadienyl Tricarbonyl Rhenium Complexes

“…There have been recent efforts devoted to the preparation of η 5 -cyclopentadienyl-tricarbonyl-technetium CpTc(CO) 3 and rhenium CpRe(CO) 3 complexes, , since they present favorable structural and chemical features (small size, low polarity, high stability) and are very different from inorganic complexes of these metals. , However, up until now the preparation of these organometallic species has been cumbersome and has required rather harsh conditions . As far as physical and chemical properties are concerned, technetium and rhenium are very similar . Therefore, reactions involving the stable natural isotopes 185 Re and 187 Re can be reliably studied as models for the radioisotopes 186 Re/ 188 Re as well as for 99m Tc.…”

Boronic Acids in the Three-Component Synthesis of Carbon-Substituted Cyclopentadienyl Tricarbonyl Rhenium Complexes

“…We recently reported a new “three-component” synthesis that provides a convenient way for preparing halo-, carbonyloxy-, and hydroxy-substituted CpRe(CO) 3 complexes by a one-pot reaction of diazocyclopentadiene (C 5 H 4 N 2 ), a rhenium(I) tricarbonyl species ( 2 , Scheme ) and a nucleophile (halide or carboxylate anions) (Scheme , eq a ). The rapidity and simplicity of this reaction made it a promising method for labeling biologically interesting compounds with Re-186, Re-188, and Tc-99m radionuclides . However, so far the functionality linking the organic portion and the metal complex has been limited to an ester group (Scheme , eq a ), which in some cases might undergo a hydrolytic cleavage when used in vivo .…”