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Reactions of [Re(NPhF)Cl 3 (PPh 3 ) 2 ] ({NPhF} 2− = p -fluorophenylimide) with a variety of alkyl and aryl isocyanides have been studied. Different reactivity patterns and products have been obtained depending on the steric and electronic properties of the individual ligands. This involves the formation of 1 : 1 and 1 : 2 exchange products of Re( v ) with the general formulae mer -[Re(NPhF)Cl 3 (PPh 3 )(isocyanide)] and cis - or trans -[Re(NPhF)Cl 3 (isocyanide) 2 ]. The stability of the obtained products is correlated with the substitution pattern of the isocyanide ligands. The products have been studied by single-crystal X-ray diffraction and spectroscopic methods, including IR and multinuclear NMR spectroscopy as well as mass spectrometry. The use of partially fluorinated starting materials and ligands allows the modulation of the solubilities of the starting materials and the products as well as the monitoring of the reactions by means of 19 F NMR. The attachment of the CF 3 or F substituent on the isocyanides gives control over the steric bulk and the electronic properties of the ligands and, thus, their reactivity. 

Organometallic approaches are of ongoing interest for the development of novel functional 99mTc radiopharmaceuticals, while the basic organotechnetium chemistry seems frequently to be little explored. Thus, structural and reactivity studies with the long-lived isotope 99Tc are of permanent interest as the foundation for further progress in the related radiopharmaceutical research with this artificial element. Particularly the knowledge about the organometallic chemistry of high-valent technetium compounds is scarcely developed. Here, phenylimido complexes of technetium(V) with different isocyanides are introduced. They have been synthesized by ligand-exchange procedures starting from [Tc(NPh)Cl3(PPh3)2]. Different reactivity patterns and products have been obtained depending on the steric and electronic properties of the individual ligands. This involves the formation of 1:1 and 1:2 exchange products of Tc(V) with the general formulae [Tc(NPh)Cl3(PPh3)(isocyanide)], cis- or trans-[Tc(NPh)Cl3(isocyanide)2], but also the reduction in the metal and the formation of cationic technetium(I) complex of the formula [Tc(isocyanide)6]+ when p-fluorophenyl isocyanide is used. The products have been studied by single-crystal X-ray diffraction and spectroscopic methods, including IR and multinuclear NMR spectroscopy. DFT calculations on the different isocyanides allow the prediction of their reactivity towards electron-rich and electron-deficient metal centers by means of the empirical SADAP parameter, which has been derived from the potential energy surface of the electron density on their potentially coordinating carbon atoms. 

p‐Fluorophenylisocyanide (CNPh^pF) reacts with [Re(CO)₅Br] under stepwise exchange of the carbonyl ligands depending on the conditions applied. The reaction stops with the formation offac‐[Re(CO)₃Br(CNPh^pF)₂] in boiling THF. An ongoing carbonyl exchange is observed at higher temperatures, e. g. in refluxing toluene, with the final formation of the [Re(CNPh^pF)₆]⁺cation. The progress of the reactions has been studied by¹⁹F NMR spectroscopy and the structures of [Re(CO)Br(CNPh^pF)₄] and [Re(CNPh^pF)₆](BPh₄) have been elucidated by X‐ray diffraction.

 

Eine erste konsistente Serie einkerniger 17‐Elektronenkomplexe von drei Elementen der Gruppe 7 wurde in kristalliner Form hergestellt und durch Röntgenkristallstrukturanalyse sowie spektroskopische Methoden untersucht. Die paramagnetischen Verbindungen der Zusammensetzung [M⁰(CO)(CNp‐F‐Ar^DArF2)₄] (M=Mn, Tc, Re; Ar^DArF2=2,6‐(3,5‐(CF₃)₂C₆H₃)₂C₆H₂F)) werden durch jeweils vier sterisch anspruchsvolle Isocyanid‐Liganden stabilisiert, wodurch auch eine Dimerisierung der Metalloradikale verhindert wird. Die Verbindungen besitzen eine quadratisch‐pyramidale Struktur mit jeweils einem Carbonyl‐Liganden als Apex. EPR‐Spektren der Technetium‐ und Rheniumverbindungen zeigen eine deutliche Anisotropie mit großen⁹⁹Tc und^185,187Re‐Hyperfeinstrukturkopplungen für jeweils eine der Komponenten. Für die Bestimmung der EPR‐Parameter des entsprechenden Mn⁰‐Komplexes wurde Hochfeld‐EPR (Q‐Band und W‐Band) verwendet.

 

The first consistent series of mononuclear 17‐electron complexes of three Group 7 elements has been isolated in crystalline form and studied by X‐ray diffraction and spectroscopic methods. The paramagnetic compounds have a composition of [M⁰(CO)(CNp‐F‐Ar^DArF2)₄] (M=Mn, Tc, Re; Ar^DArF2=2,6‐(3,5‐(CF₃)₂C₆H₃)₂C₆H₂F) and are stabilized by four sterically encumbering isocyanides, which prevent the metalloradicals from dimerization. They have a square pyramidal structure with the carbonyl ligands as apexes. The frozen‐solution EPR spectra of the rhenium and technetium compounds are clearly anisotropic with large⁹⁹Tc and^185,187Re hyperfine interactions for one component. High‐field EPR (Q band and W band) has been applied for the elucidation of the EPR parameters of the manganese(0) complex.

 

The mixed isocyanide/carbonyl complexes cis - and trans -[Re(CO) 3 Br(CNAr Dipp2 ) 2 ] (Ar Dipp2 = 2,6-(2,6-(i-Pr) 2 C 6 H 3 ) 2 C 6 H 3 ) can be synthesized from reactions of [Re(CO) 5 Br] and CNAr Dipp2 depending on the conditions applied. Reduction of the neutral Re( i ) species gives the monoanionic complex [Re(CO) 3 (CNAr Dipp2 ) 2 ] − or the neutral [Re(CO) 3 (CNAr Dipp2 ) 2 ], which contain rhenium in the formal oxidation states “−1” and “0”, respectively.