Solvent-Dependent Access to Two Different Ni4 II Core Topologies from the First Use of Pyridine-2,6-dimethanol in Nickel(II) Cluster Chemistry

The use of pyridine-2,6-dimethanol, pdmH2, in reactions with nickel(II) acetate has led to two Ni4 clusters, depending on the solvent. [Ni4(O2CMe)4(pdmH)4]MeCN (1MeCN) can be obtained from MeCN and [Ni4(O2CMe)6(pdmH)2(EtOH)2] 1.2EtOH (21.2EtOH) fromEtOH. Each cluster can be converted into the other in the appropriate solvent. The tetranuclear cluster molecule 1 possesses a distorted cubane {Ni4(m3-OR)4} 4þ core (RO pdmH) with the NiII atoms and the alkoxide-type oxygen atoms from the Z3:Z1: m3 pdmH ligands occupying alternate vertices of the cube; four Z1:Z1: m MeCO2 groups cap four faces of the cube. The four NiII atoms in molecule 2 are located at four vertices of a defective dicubane and are bridged by six oxygen atoms, two m3 from the Z 3:Z1:Z1: m3 pdmH ligands and four from four monoatomically bridging MeCO2 groups; peripheral ligation is provided by two Z1:Z1: m MeCO2 groups and two terminal EtOH ligands. IR data are discussed in terms of the coordination modes of the ligands. Variable-temperature direct-current magnetic susceptibility data of 1 and 2 were modelled with two and three J values respectively, indicating diamagnetic ground states (S 0). The sign and the magnitude of the J values are discussed in terms of structural features of the complexes