Three octanuclear phosphonate clusters, formulated as [Ln8(O3P(t)Bu)6(μ3-OH)2(H2O)2(HO(i)Bu)(O2C(t)Bu)12](NH3(i)Pr)2 (Ln = Gd, Dy and Tb), were synthesised by refluxing a mixture of pivalic acid (HO2C(t)Bu), Ln(NO3)3·6H2O, tert-Butyl phosphonic acid (H2O3P(t)Bu) and isopropylamine ((i)PrNH2) in isobutyl alcohol (i)BuOH.