EXAMPLE OF PSEUDO 5-COORDINATION IN COPPER(II) COMPLEXES

A series of potential pentadentate bicyclic macrocyclic ligands has been prepared by the nucleophilic addition of various dialkoxides to the copper(II) complex of tetrabenzo[b,f, J, A] [1, 5, 9, 13]tetraazacyclohexadecine (TAAB). The resulting complexes can be classified as pseudo square pyramidal with potential N4S, N4N', and N4O donor sets with S, N', and O occupying the axial coordination position. The complexes are all monomeric exhibiting characteristic magnetic moments for an S=1/2 system in the solid state. The optical spectra, as well as the X-band ESR spectra of the five donor atom macrocyclic Cu(II) complexes, are essentially identical while Q-band ESR data indicate a very slight variation in symmetry among the series. The spectroscopic differences between Cu(TAAB)2+, a nonbridged four-coordinate Cu(TAAB)(OCH3)2 compound, a bridged four-coordinate Cu(TAAB)[O(CH2)5O] compound, and the five-coordinate series Cu(TAAB)[O(CH2)2X(CH2)2O] (X=S, NCH3, O) compounds are discussed in terms of both a “cage effect” and the potential effect of the axial donor atom. © 1979, American Chemical Society. All rights reserved.