ω-Nitroacetophenone as a chelating agent. Part V. The Lewis acid-base interaction of bis(ω-nitroacetophenonato)copper(II) in solution with several heterocyclic and other N-bases

Abstract

The interaction of bis(ω-nitroacetophenonato)copper(II), [Cu(ω-nap)₂] with γ- and α-picoline in non-donor solvents has been studied in detail in the rang O ⩽R⩽∞(where R is the molar ratio N-base/Cu). For both N-bases the observed spectral changes in the region 7·0–25·0 kk are consistent with the occurrence of two distinct successive reactions which lead to the formation, first of the five-co-ordinate (presumably square pyramidal) 1:1 adducts, and then to the pseudo-octahedral 1:2 adducts. Electronic absorption spectra show that the previously reported 1:1 tris-chelate adducts formed by Cu(ω-nap)₂ with α,α′-bipyridyl and o-phenanthroline retain their pseudo-octahedral structure in solution with non-interacting solvents; in these solvents the 1:2 adducts from pyridine, benzylamine, and aniline dissociate to give mainly the 1:1 (five-co-ordinate) adducts, whereas that from aniline dissociates to give predominantly Cu(ω-nap)₂. An approximate scale of relative stability in solution of the base adducts studied is given, together with an account of the relative tendency to attain six-co-ordination of Cu(ω-nap)₂ and a series of copper(II)β-diketone chelates.