Scheme 1: Three-step reaction of compound 1.

X-ray crystal structure analysis; TGA Literature

Complex 1 [CoII10(OH)2(bda)6(ib)6] crystallizes in the triclinic space group P-1. Its molecular structure (figure 1) displays a planar decanuclear cobalt(II) metal core. It consists of ten octahedrally coordinated Co(II) ions, six bda2– ligands, six ib– ligands and two OH– groups. The oxidation states of the cobalt atoms are established by bond valence sum analysis [Σbv(CoII) = 1.89 – 1.97] and they are in agreement with charge neutrality arguments of coordination cluster.
In the molecular structure six Co(II) ions are in a NO5 and four in an O6 environment. Co2, Co4, Co2´ and Co4´ are highly distorted, with one unusual long Co–Oib bond of each (Co2–O6, 2.466(3) Å and Co4–O11, 2.363(3) Å), which are about 0.3 Å longer than the other Co–Oib bonds. Co1 binds to both OH– groups, and to four µ4-O-atoms of four different bda2– ligands. It is connected with Co2, Co3, Co1´, Co3´, Co4´ and Co5´ through these oxo bridges. Co2 is chelated by one bda2– ligand through its N- and O-atoms. The coordination sphere of Co2 is filled by one ib– ligand and one µ4-O-atom of an ethoxide rest of a second bda2– ligand. Co3 is coordinated by one bda2– ligand in a chelating fashion. It binds to one OH– group (Co3–O1: 2.146(3) Å) and the coordination sphere is filled by two µ3-Obda-atoms of two different bda2– ligands. The coordination of Co4 is similar to this of Co2, and differs only in the bond length. Co5 binds to three isobutyrate ligands, one is chelating the Co5 atom, and to one O-atom of the remaining two. The octahedral coordination is filled by two µ4-Obda-atoms, which lead to an O6 coordination environment.