Initial use of the di-2-pyridyl ketone/sulfate “blend” in 3d-metal cluster chemistry: Preparation, X-ray structures and physical studies of zinc(II) and nickel(II) cubanes

The use of di-2-pyridyl ketone ((py)2CO)/sulfate “blend” in nickel and zinc chemistry has yielded the neutral cubane clusters [Ni4(SO4)2{(py)2C(OH)O}4]·4MeOH·3H2O (1·4MeOH·3H2O) and [Zn4 (SO4)2{(py)2C(OH)O}4 (H2O)2]·6H2O (2·6H2O). The preparation of the two complexes was achieved by the reaction of MSO4·×H2O [M = Ni, x = 6 (1); M = Zn, x = 7 (2)] with (py)2CO and LiOH·H2O in MeOH/H2O (for both complexes) or MeOH/MeCN (only for 1). The structures of both compounds have been determined by single-crystal X-ray crystallography. Di-2-pyridyl ketone exists in its monoanionic gem-diol form and functions as an η1:η3:η1:μ3 ligand. Both complexes have been characterized by spectroscopic techniques (IR, Raman). Thermal decomposition (TG, DTG and DTA) data for 2 are also discussed. The magnetic properties of 1 have been studied by variable-temperature dc magnetic susceptibility techniques. The studies indicate both ferromagnetic and antiferromagnetic coupling between the four NiII atoms. A three-J model was found to be adequate for describing the thermal variation of the molar magnetic susceptibility.