COMPLEXES AS LIGANDS .2. STRUCTURAL, SPECTRAL, AND MAGNETIC-PROPERTIES OF THE BIMETALLOMER FORMED FROM N,N'-ETHYLENEBIS(SALICYLIDENIMINATO)COPPER(II) AND BIS(HEXAFLUOROACETYLACETONATO)COPPER(II)

As a continuation of our studies of complexes as ligands, we have investigated the bimetallomer Cu(salen)Cu(hfac)2, which is the adduct formed by the reaction of the Lewis base N, Nʹ-ethylenebis(salicylideniminato)copper(II) with the Lewis acid bis(hexafluoroacetylacetonato)copper(II). Since this bimetallomer contains two different copper(II) environments (six-coordinate and four-coordinate), magnetic susceptibility and EPR spectral studies were undertaken in order to characterize the system. Variable-temperature magnetic susceptibility measurements indicate an antiferromagnetic exchange interaction with a coupling constant, J, between the copper(II) centers of -20.4 cm-1. In order to explain the relatively small value of J when compared to that of symmetric copper(II) bimetallomers, a single-crystal X-ray diffraction study was carried out. The compound crystallizes in the triclinic space group P1 with four molecules in the unit cell. The reduced cell parameters are a = 17.03 (4) Å,b= 19.11 (4) Å, c = 9.89 (2) Å, a = 96.58 (11)°, β = 100.10 (16)°, and 7 = 107.70 (13)°. The structure was refined by full-matrix least-squares methods to a weighted R factor of 0.074 for data with F0 ≥ 3σF. The structural results indicate that the reduced value of J is due to the low symmetry of the bridge area which allows for only one phenolic oxygen to participate in the superexchange pathway. © 1979, American Chemical Society. All rights reserved.