Synthesis, structure and properties of {M4O4} cubanes containing nickel(ii) and cobalt(ii)

Abstract

A survey of the crystal structures containing simple {M₄O₄} cubane units is reported. It shows that the average M–M distance in these complexes is relatively constant for a given metal ion M. The structures are all distorted from the idealised cube to a T_d structure, and most show a further distortion which, however, usually maintains some elements of symmetry. A system for classifying the different types of ligand in these complexes is proposed. Two new cubanes of cobalt(II) and nickel(II) with the ligand (R,R)-bis-1,2-(1-methylbenzimidazol-2-yl)ethane-1,2-diol, (R,R)-1 or its enantiomer have been isolated and the crystal structure of the cobalt(II) complex confirms the cubane structure. Electronic, CD and ¹H NMR spectra and magnetic susceptibility data are reported. The magnetic data for these and other compounds in the literature are discussed in terms of the structural parameters.