A polynucleating oxygen donor ligand based on condensation of p-chlorophenylstibonic acid (ArSbO(3)H(2)) and t-butylphosphonic acid is reported. [(SbAr)(2)O(HO(3)P(t)Bu)(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, [Cu(4)O(2)(SbAr)(2)(O(3)P(t)Bu)(2)(O(2)CMe)(2)(OMe)(6)], with the four copper centres arranged in a rhombus; a minor product is a tricopper complex, [Cu(3)O(4)(SbAr)(2)(O(3)P(t)Bu)(4)(py)(3)]. With LiOMe as base the major product is again the tetranuclear cage, but the minor product is a heterometallic cage, [Cu(5)Li(4)O(6)(SbAr)(4)(O(3)P(t)Bu)(6)(O(2)CMe)(2)(OMe)(4) (MeOH)(4)]. With 2,6-lutidine as base an octametallic complex is formed, [Cu(8)O(4)(SbAr)(2)(O(3)P(t)Bu)(6)(O(2)CMe)(4)(lutidine)(2)]. Magnetic studies show both anti-ferromagnetic and weak ferromagnetic exchange between the copper centres in these new complexes.