Synthesis and structural and magnetic characterisation of copper(II) complexes of mixed phosphonate-antimonate ligands

A polynucleating oxygen donor ligand based on condensation of p-chlorophenylstibonic acid (ArSbO3H2) and t-butylphosphonic acid is reported. [(SbAr)(2)O((HO3PBu)-Bu-t)(6)] contains two antimony centres, bridged by an oxide and two hydrogen phosphonates. Reaction with copper acetate under solvothermal conditions produces four new polymetallic copper complexes. With pyridine used as a base the major product is a tetracopper cage, [Cu4O2(SbAr)(2)((O3PBu)-Bu-t)(2)(O2CMe)(2)(OMe)(6)], with the four copper centres arranged in a rhombus; a minor product is a tricopper complex, [Cu3O4(SbAr)(2)((O3PBu)-Bu-t)(4)(py)(3)]. With LiOMe as base the major product is again the tetranuclear cage, but the minor product is a heterometallic cage, [Cu5Li4O6(SbAr)(4)((O3PBu)-Bu-t)(6)(O2CMe)(2)(OMe)(4) (MeOH)(4)]. With 2,6-lutidine as base an octametallic complex is formed, [Cu8O4(SbAr)(2)((O3PBu)-Bu-t)(6)(O2CMe)(4)(lutidine)(2)]. Magnetic studies show both anti-ferromagnetic and weak ferromagnetic exchange between the copper centres in these new complexes.