Synthesis and characterization of a novel cyclic tetranuclear CoII4 cluster consisting of a quadrilateral core

A novel cyclic tetranuclear cluster, [Co(H2O)6][Co4(ccdp)2(H2O)4]·8H2O·2CH3CN (1) with cobalt(II) ions sitting in a quadrilateral has been synthesized and fully characterized by exploiting the flexibility, chelating ability and bridging potential of a carboxylate rich dinucleating ligand, H5ccdp [H5ccdp = N,N′-Bis[2-carboxybenzomethyl]-N,N′-Bis[carboxymethyl]-1,3-diaminopropan-2-ol]. The crystal structure of 1 contains a [Co4II(H2O)4)]2– core unit which is held together by two bridging benzoate potions of the ligands, ccdp5–. Furthermore, the [Co4II(H2O)4)]2– core unit is stabilized and charge neutralized by intermolecular hydrogen bonding and [Co(H2O)6]2+, respectively.