Trinuclear Ni(II) Complex with Rare Deprotonation of the Bridging Oxamate and Imino Nitroxide Radical as Blocking Ligand

Phenylene-based bis-oxamate polydentate ligands offer unique opportunities for creating a large variety of coordination compounds in which paramagnetic metal ions are strongly magnetically coupled. The employment of iminonitroxyl (IN) radicals as supplementary ligands confers numerous benefits, including the strong ferromagnetic interaction between Ni and IN. Furthermore, the chelating IN can function as a blocking ligand, thereby impeding the formation of coordination polymers. In this study, we present the molecular, crystal structure, experimental, and theoretical magnetic behavior of an exceptional neutral trinuclear complex [Ni(L3−)2(IN)3]∙5MeOH (1) with a cyclic triangular arrangement. Moreover, in this compound three Ni2+ ions are linked by the two bis-oxamate ligands playing rare tritopic function due to an unprecedented triple deprotonation of the related meta-phenylene-bis(oxamic acid). Despite the presence of six possible magnetic couplings in the three-nuclear cluster 1, its behavior was reproduced well using a three-J model and ZFS, under the assumption that the three different Ni-IN interactions are equal to each other, whereas only two equivalent in value Ni-Ni interactions are taken into account, and the third one was equated to zero. These studies indicate the presence of two opposite in nature type of magnetic interactions within triangular core. DFT and CASSCF/NEVPT2 calculations were completed to support the experimental magnetic data simulation.