Conversion of tetranuclear Ni complexes from a defect dicubane core to a [Ni4O4] cubane-like core via addition of 2-hydroxymethylpyridine: Synthesis, crystal structures, and magnetic properties

A defect dicubane-like complex, [Ni4{(2-py)2C(OH)O}2{(2-py)2C(OCH3)O}2 (N3)4]·2CH3CN·2H2O (1) and a cubane-like complex, [Ni4{(2-py)2C(OH)O}3(hmp)3(NO3)].(NO3)·3H2O (2) (Hhmp = 2-hydroxymethylpyridine), were prepared by reacting NiCl2·6H2O with (py)2CO, NaN3 and NMe4OH in MeOH/MeCN and the similar reaction exception the N3− anion replaced by multidentate chelating ligand Hhmp, respectively. X-ray analysis revealed that four Ni2 + ions, four O atoms and two N atoms in 1 were located at the vertices of a defect dicubane; by contrast, four Ni2 + ions and four O atoms in 2 occupied alternate vertices of a [Ni4O4] cubane. Magnetic studies indicated the presence of overall ferromagnetic interactions between Ni2 + ions within both complexes.