On the Structure, Electrochemistry, and Spectroscopy of the (N,N‘-Bis(2‘-(dimethylamino)ethyl)-N,N‘-dimethylpropane-1,3- diamine)copper(II) Ion

The synthesis, spectroscopy, and electrochemistry of the acyclic tertiary tetraamine copper(II) complex [CuL¹](ClO₄)₂ (L¹ = N,N‘-bis(2‘-(dimethylamino)ethyl)-N,N‘-dimethylpropane-1,3-diamine) is reported. The X-ray crystal structure of [CuL¹(OClO₃)₂] reveals a tetragonally elongated CuN₄O₂ coordination sphere, exhibiting relatively long Cu−N bond lengths for a Cu^II tetraamine, and a small tetrahedral distortion of the CuN₄ plane. The [CuL¹]²⁺ ion displays a single, reversible, one-electron reduction at −0.06 V vs Ag/AgCl. The results presented herein illustrate the inherent difficulties associated with the separation and characterization of Cu^II complexes of tertiary tetraamines, and some previously incorrect assertions and unexplained observations of other workers are discussed.