Three aspects of group 7 isocyanide chemistry were considered in this thesis. First, the reactivity of electron-poor isocyanides with facial tricarbonyl starting materials was investigated. As expected, the reactions with technetium were significantly faster than with rhenium and carbonyl ligands of fac-[Tc(CO)3(CNR)2Cl] (R = tBu, nBu) could be exchanged under thermal conditions forming the key intermediate mer-[Tc(CNp-FArDArF2)3(CNR)2Cl]. The chlorido ligand in this compound can be abstracted using a halide scavenger and replaced by a sixth isocyanide ligand leading to the first defined heteroleptic hexakis(isocyanide)technetium(I) complex : [Tc(CNp-FArDArF2)3(CNnBu)2(CNtBu)][PF6]. CNPhpF was then used to assess the reactivity of electron-poor isocyanides without the sterical strain caused by the flanking rings of the m,m´-terphenyl isocyanide CNp-FArDArF2. The reaction kinetics were even faster once the sterical strain was removed. In both cases, the combination of 99Tc and 19F NMR spectroscopy proved invaluable to monitor the progress of the reaction in solution. The use of 19F NMR was even more important for reaction involving rhenium as the metal center cannot be observed by NMR. The slower reaction rates of the rhenium compounds allowed the facile isolation of intermediate compounds such as fac-[Re(CO)3(CNPhpF)2Br] or trans-[Re(CO)(CNPhpF)4Br], which could both only be spectroscopically observed for technetium. In a second part of the thesis, the reactivity of isocyanides with high-valent phenylimido starting materials was studied. Both electronic and steric factors play a role in the outcomes of the reactions. The electron-deficient CNPhpF was able to cleave the technetium-nitrogen bond and replaced the entire coordination sphere to form a hexakis(isocyanide)technetium(I) complex. Such a high substitution degree was not observed for rhenium and only a [Re(NPhF)(PPh3)(CNPhpF)Cl3] complex could be obtained. On the other hand, the electron-rich m,m´-terphenyl isocyanides CNArDipp2 and CNArTripp2 were able to form bis(isocyanide) complexes with both metals. The reactions with [Re(NPhF)Cl3(PPh3)2] also show, which role fluorine-substitution may have in the coordination chemistry. The non-fluorinated starting material [Re(NPh)Cl3(PPh3)2] is too little soluble for reactions with delicate isocyanides and the introduction of a fluorine atom on the phenylimido ring increases the solubility. Furthermore, this fluorine atom shows small, but significant shifts in 19F NMR resonances, which were used to monitor the progress of such reactions. Moreover, the electron deficient and highly fluorinated CNp-FArDArF2only forms [M(NPhR)Cl3(PPh3)(CNp-FArDArF2)], even though the sterical hinderance of the ligand does not preclude a higher substitution. Remarkably, the IR stretches of all used isocyanides show hypsochromic shift upon coordination on Re(V) and Tc(V) centers. This means, they act exclusively as σ-donors. In the last part of this thesis, the gained knowledge on the influence of steric and electronic parameters on the reactivity of isocyanide ligands was applied to synthesize a functionalizable isocyano ligand. Surface-Averaged Donor−Acceptor Potential (SADAP) parameters showed that the alkyne functionalized isocyanide CNPhpC≡CH should have a similar reactivity to the CNPhpF ligand, which replaces carbonyl ligands under thermal conditions. Indeed, the reaction of (NBu4)[Tc2(µ-Cl)3(CO)6] with CNPhpC≡CH lead to the (hexakis)isocyanide complex [Tc(CNPhpC≡CH)6]+. The latter complex could be “clicked” with benzyl azide using an appropriate copper catalyst. The reaction conditions to form the (hexakis)isocyanide complex were harsh and required an inert atmosphere which precluded equivalent reactions with aqueous 99mTc. The Cu(I) complex [Cu(CNPhpC≡CH)4](BF4) could be readily synthesized and “clicked” under milder conditions. The resulting [Cu(CNPhazole)4]+ can be used as a transmetalation reagent for the synthesis of the hexakis(isocyanide)technetium(I) complex, which is the preferable approach for the synthesis of the technetium complex with the short-lived isotope 99mTc. Alternatively, the uncoordinated ‘Click’ product can be obtained by cleaving the [Cu(CNPhazole)4](BF4) complex with aqueous NaCN. It readily reacts with mer-[Tc(CO)3(tht)(PPh3)2](BF4) (tht = tetrahydrothiophene) under the exchange of the thioether ligand.
