Ni5, Ni8, and Ni10 Clusters with 2,6-Diacetylpyridine-dioxime as a Ligand

In the present work, novel coordination possibilities for the system dapdoH2/NiII (dapdoH2 = 2,6-diacetylpyridine-dioxime) have been explored. Depending on the starting reagents and solution conditions, several clusters with nuclearities ranging from Ni5 to Ni10 were achieved and structurally characterized, namely, [Ni5(R-COO)2(dapdo)2(dapdoH)2(N(CN)2)2(MeOH)2] in which R-COO– = benzoate (1) or 3-chlorobenzoate (2), [Ni8(dapdo)4(NO3)4(OH)4(MeOH)4] (3), and [Ni10(dapdo)8(N(CN)2)2(MeO)(MeOH)](NO3) (4). For the first time, pentadentate coordination for the dapdo2– ligand has been established. All compounds show a combination of square-planar and octahedrally coordinated nickel atoms. According to the Ni2(sp)Ni3(Oh) (1 and 2), Ni4(sp)Ni4(Oh) (3), and Ni4(sp)Ni6(Oh) (4) environments, these systems magnetically behave as trimer, tetramer, and hexanuclear clusters, respectively. dc magnetic measurements in the 2–300 K range of temperature reveal antiferromagnetic coupling for all compounds, and the correlation of the superexchange interaction with the torsion angles involving the oximato bridges is experimentally confirmed.