Monomer and dimer complexes of copper acetate with pyridine and picolines. part I. Synthesis and characterization

Abstract

Synthetic investigations of copper( II) acetate addition compounds with pyridine and pico/ines have led to the isolation of the 1:2 adducts with pyri­dine and 'Y-picoline in addition to the known dimeric 1:1 adducts. The two new compounds have magnetic moments and electronic and epr spectral properties characteristic of monomeric copper complexes. Solutions of the dimeric 1:1 adducts with pyridine, (J- and 'Y-picoline in their respective ligands have spectral and magnetic properties identical to those of the monomers, while traces of the dimer persist in solutions of the a-picoline analog. This is discussed in terms of the steric requirements of the ligands. The large nmr isotropic shift of the acetate-methyl protons in solutions of the dimeric complexes suggests a greater contribution from superexchange mechanism to the magnetic coupling. Isotropic shifts of coordinated ligands in solutions of the monomeric complexes are analyzed and the contact contributions are discussed in terms of o'- and rr- delocalization mechanisms.