Dicubane-like tetrameric cobalt(II)-pseudohalide ferromagnetic clusters

Three tetrameric cobalt(II)-pseudohalide complexes have been structurally a nd magnetically characterized. Compounds I and 2 are isomorphous and exhibi t the general formula [CO2(dpk . OH)(dpk . CH3O)(L)(H2O)](2)A(2). 4H(2)O wh ere dpk = di-2-pyridyl ketone, L = N-3(-) and A = BF4- for 1, and L = NCO- and A = ClO4- for 2. The ligands dpk . OH- and dpk . CH3O- result from solv olysis and ulterior deprotonation of dpk in water and methanol, respectivel y. Both compounds exhibit cationic tetramers consisting of a dicubane-like core with two missing vertexes where the Co(Il) ions are connected through end-on pseudohalide and oxo-bridges. A similar , tetranuclear core has been found for 3 whose formula is [Co-2(dpk . OH)(dpk . CH3O)(NCO)(2)](2). In t his case, the tetramers are neutral and exhibit a terminal cyanate in place of the coordinated molecule of water for 1 and 2. The tetrameric units for 2 and 3 represent the first examples of any kind of cubanes exhibiting cya nate bridges as well as the first Co(II) compounds exhibiting intermetallic bridges through these pseudohalide. groups. Measurements of the magnetic s usceptibility indicated the presence of ferromagnetic Co-II-Co-II interacti ons in the three compounds.