Synthesis and Characterization of Variable-valent Imidorhenium Species. A Family of Imidorhenium(VI) Amide Complexes and their Imidorhenium(V) Imine Precursors Related by Oxygen Atom Transfer

The synthesis of imidorhenium(V) [Re(NAr)Cl₃(L)] complexes is reported. Their reaction with dilute HNO₃ furnishes [Re(NAr)Cl₃(L′)] species incorporating monoionized iminoamide ligands (the ligands are abbreviated as L and L′ respectively). The iminoamide complexes exhibit sextet EPR spectra in CH₂Cl₂ solution at room temperature. They are electroactive in MeCN solution and to display two quasi reversible responses near 0.2 and 1.6 V which can be attributed to Re^V→Re^VI and Re^VI → Re^VII oxidations respectively. One of the [Re(NAr)Cl₃(L)] complexes has been structurally characterized. The trans influence of the amide nitrogen considerably lengthens the Re–N bond lying trans to the imido group. The triply bonded ReN–C moiety is linear.