Solvent-dependent access to two different Ni4II core topologies from the first use of pyridine-2,6-dimethanol in nickel(II) cluster chemistry

Abstract

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 (1·MeCN) can be obtained from MeCN and [Ni 4(O2CMe)6(pdmH)2(EtOH)2]1.2EtOH (21.2EtOH) from EtOH. Each cluster can be converted into the other in the appropriate solvent. The tetranuclear cluster molecule 1 possesses a distorted cubane {Ni4(μ3-OR)4}4+ core (RO-=pdmH-) with the NiII atoms and the alkoxide-type oxygen atoms from the η3:η1: μ3 pdmH- ligands occupying alternate vertices of the cube; four η1:η1: μMeCO2- 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 μ3 from the η3:η1: η1:μ3 pdmH- ligands and four from four monoatomically bridging MeCO2- groups; peripheral ligation is provided by two η1:η1:μ MeCO 2- 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. © 2012 CSIRO.