Formal encapsulation of [Fe(H2O)6]^3+ by {Fe2(hpdta)} units gives a system of S= 13/2 FeIII9 oxo clusters showing magnetic hysteresis

Under solvothermal conditions the unprecedented nonanuclear FeIII aggregate [Fe9((mu)3-O)4((mu)-OH)4(hpdta)4]5– is formed through the formal encapsulation of [Fe(H2O)6]3+ by four [Fe2(hpdta)(H2O)2]+ units: the aggregates have ground state spins of S= 13/2 while the observed hysteresis below 1.8 K results from inter-cluster antiferromagnetic coupling.