Further Structural and Magnetic Studies of Tricopper Dipyridylamido Complexes

The compound Cu3(dpa)4Cl2, 1 (dpa = the anion of dipyridylamine), which was first synthesized and characterized in 1990, has been structurally characterized in three new crystal forms having Cu···Cu separations of 2.47−2.49 Å. Its magnetic properties have been studied fully. Reaction of Cu3(dpa)4Cl2 with 2 equiv of silver tetrafluoroborate yields Cu3(dpa)4(BF4)2 (2), a compound with a similar linear trinuclear structure but coordinated BF4 anions in each axial position and having shorter Cu···Cu distances of 2.40 Å but similar magnetic properties. Least squares fitting of the magnetic susceptibility data for 1 and 2 gave isotropic g values of 2.007 and 2.130 and exchange parameters of −373 and −411 cm-1, respectively. This suggests the possible existence of an exchange pathway in which the metal atoms interact directly with each other.