A Mono-Diazenide Complex from Perrhenate: Toward a New Core for Rhenium Radiopharmaceuticals

A new method for the synthesis of low to intermediate oxidation
state rhenium complexes containing a bifunctional ligand has been
developed. Reaction of [ReO4]- with substituted phenylhydrazines
and triphenylphosphine in acetonitrile in the presence of HCl allows
the isolation of [ReCl2(NNC6H4-4-R)(NCCH3)(PPh3)2] (where R =
OCH3, Cl, or CO2CH3). The substituted hydrazine acts as both a
reductant and source of a monodentate diazenide ligand. The
compounds have all been characterized in the solid state by X-ray
crystallography and in the solution state by NMR, electrospray
mass spectrometry, and HPLC. Cyclic voltammetry measurements
show that the mono-diazenide complexes undergo a reversible
oxidation.