Self-assembled nickel cubanes as oxygen evolution catalysts

Ni₄O₄ cubanes [(μ₃-L¹O)NiCl(MeOH)]₄ (1) and [(μ₃-L²O)NiCl(H₂O)]₄ (2) (L¹OH = 1-H-2-benzimidazolylmethanol, L²OH = 1-methyl-2-benzimidazolylmethanol) self-assemble from commercially available 1-H- and 1-methyl-2-benzimidazolylmethanol and NiCl₂·6H₂O in high yields under mild conditions. Both complexes were characterised spectroscopically and by X-ray crystallography. The cubanes oxidise water electrocatalytically to dioxygen at neutral pH in aqueous potassium phosphate buffer solutions.