MEDIUM-RING COMPLEXES .3. A COMPARISON OF PLANAR AND PYRAMIDAL COPPER(2) AND PLANAR NICKEL(2) COMPLEXES CONTAINING 7- AND 8-MEMBERED-RING DIAMINES

The spectral properties of planar complexes of copper(II) and nickel(II) with 1,5-diazacyclooctane (daco)are compared to planar nickel(II) and planar and pyramidal copper(II) complexes with 1,4-diazacycloheptane (dach). The geometry of the chelate rings in the bis-dach complexes is discussed and the effects of conversion of Cu(dach)2 complexes from fourto five-coordinated species are analyzed. The planar [Cu(dach)2](C1O4)2 has a λmax in the visiblespectrum at 505 mμ whereas the pyramidal [Cu(dach)2Cl]C1O4 has a λmax near 610 mμ. When other ligands occupy the apical position of the pyramidal complex, the maximum lies between these extremes. A spectrochemical series may be established based on the shift ofthe absorption maxima to lower energy as various ligands are added to the apical position: C1O4 ~ CH3NO2 < (CH3)2CO < CH3CN < DMSO ~ KO3 < H2O < HCONH2 ≪ SON- ~Br- ~ Cl-. © 1969, American Chemical Society. All rights reserved.