A new mixed-valence hexanuclear cobalt complex, [Co4IICo2III(dea)2(Hdea)4)(piv)4](ClO4)2·H2O: Synthesis, crystal structure and magnetic properties

A new CoII/CoIII hexanuclear complex, [Co4IICo2III(dea)2(Hdea)4)(piv)4](ClO4)2·H2O 1, has been obtained by reacting cobalt(II) perchlorate, diethanolamine, and pivalic acid (H2dea = diethanolamine and piv = pivalato anion). The cobalt ions are held together by four μ3 and four μ2 alkoxo bridges as well as by four syn–syn carboxylato groups. The hexanuclear motif contains four Co(II) and two Co(III) ions. The {CoII4CoIII2(μ2-O)4(μ3-O)4} core can be described as a four face-sharing monovacant and bivacant distorted heterocubane units. The cobalt(III) ions are hexacoordinated. Two of the cobalt(II) are hexacoordinated, while the two others are pentacoordinated with a bipyramidal stereochemistry. The magnetic properties of 1 have been investigated in the temperature range 1.9–300 K. Compound 1 exhibits an overall antiferromagnetic behaviour with a ground singlet spin state.