The preparations and structures are described of four new polyoxostibonates, [Co(p-MeC ₆H ₄Sb) ₁₂O ₂₈{Co(H ₂O) ₃} ₄]Cl ₂₋ 6H ₂O, [Co(p-ClC ₆H ₄Sb)₁₂O ₂₈{Co(H ₂O) ₃} ₄]Cl₂₋ 22H ₂O, (PhCH ₂NMe ₃) ₂[Zn(p-ClC ₆H ₄Sb) ₁₂O ₂₈Zn ₄Cl₂•₅₄ Br ₁•₄₆]•8MeCN•H ₂O and [BaCoH ₄(p-MeC ₆H ₄Sb)O ₂₈] •5H₂O. Each of these has a framework of 12 (RSb) groups linked by 28 O atoms, with one transition metal ion in a tetrahedral site in the centre. Other metal ions are coordinated to the polyhedral faces. Three of the complexes have the ε Keggin ion geometry, while the fourth is a δ isomer.