A cationic tetranuclear [NiII4(MeOH)2(pko)6]2+ cluster showing antiferro- and ferromagnetic features

The majority of reported nickel tetranuclear clusters have a dicubane-like structural core. The compound presented here is the second example possessing an Ni4O2 core based on a chair or butterfly "out-of-face" topology. This compound also belongs to the family of compounds characterized as metallacrowns with an [Ni-N-O-](n) linkage and is the only example with three Ni-O-N-Ni strands bridging the nickel atoms. The values obtained from the fitting procedure are J(1) = 55.8 cm(-1), J(2) = -67.2 cm(-1), g = 2.2, p = 1.1%. These values suggest the presence of both ferromagnetic and antiferromagnetic interactions, while a small paramagnetic impurity is also present. This magnetic behaviour with antiferromagnetic internal coupling and ferromagnetic spin-alignment is the second example in the literature and the first in the metallacrown family. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.