Equilibria between mono- and bi-nuclear complexes in Cu(O2CMe)2–pyridine derivative–diluent systems. The influence of the amine ligand basicity

Abstract

Cu(O₂CMe)₂–pyridine derivative (L) complexes [L = pyridine (py), 2-methylpyridine (2Me-py), 3,4-dimethylpyridine (3,4Me₂-py), and isoquinoline (i-quin)] have been studied by u.v. and e.s.r. spectroscopic methods. The results are interpreted in terms of the equilibrium 2[Cu(O₂CMe)₂L₂]⇌[Cu₂(O₂CMe)₄L₂]+ 2L. The relative stability of the binuclear complexes in solution strongly depends on the basicity and steric properties of the amine ligands, the tendency for adopting binuclear structures increasing in the order: 3,4Me₂-py < i-quin ≲ py < 2Me-py.