Variable temperature (303-80 K) magnetic susceptibility measurements show t
hat the exchange coupling constant J in [Cu-2(diethylenetriamine)(2) (mu -O
-acetato)(2)](PF6)(2) (1) is +79 cm(-1) indicating a ferromagnetic coupling
between the two copper(II) centers in 1. The positive sign of J is justifi
ed by qualitative molecular orbital theory which includes extended Huckel c
alculations on 1 at the X-ray crystallographically determined geometry.