Chiral Tetraamines Based on (S)-2-(Aminomethyl)pyrrolidine: Template synthesis and properties of copper(II) complexes

The template reaction of {bis[(S)-2-(aminomethyl)pyrrolidine]}copper(II) with formaldehyde, nitroethane, and base in MeOH yields optically pure {1,7-bis[(S)-pyrrolidin-2-yl]-4-methyl-4-nitro-2,6-diazaheptane}- copper(II) ([Cu((S,S)-mnppm)]²⁺) in high yield. The same reaction with rac-2-(aminomethyl)pyrrolidine is also described. Preparative details and spectroscopic and electrochemical properties of the Cu^II complexes and of the free ligands are reported and compared with structural, spectroscopic and electrochemical data of the Cu^II complex of the unsubstituted parent ligand 1,7-bis[(S)-pyrrolidin-2-yl]-2,6-diazaheptane (ppm). The crystal structure of [Cu(ppm)]Cl ClO₄ has been determined by X-ray diffraction methods.