The crystal structure of [Fe2(PIMIC6)(AnthCO2)(CH3CN)]•[Fe2(PIMIC6)(AnthCO2)(CH3CN)0.9(CH2Cl2)0.1]•[Fe2(PIMIC6)(AnthCO2)(OH2)]•0.75CH3CN: a crystallographer's nightmare or a fascinating case of disorder?

Refinement of large crystal structures as well as that of disordered structures can be challenging. If both features come together, structure refinement has the potential of becoming a crystallographer's nightmare. Here, the refinement of the large and highly disordered structure of [Fe-2(PIMIC6)(AnthCO(2))(CH3CN)]center dot[Fe-2(PIMIC6)(AnthCO(2))(CH3CN)(0.9)(CH2Cl2)(0.1)]center dot[Fe-2(PIMIC6)(AnthCO(2))(OH2)]center dot 0.75CH(3)CN [(1), PIMIC6 is a phenol-imine-based macrocycle, AnthCO(2) is an anthracene acid anion] is described and discussed. A total of 5311 parameters had to be refined to generate a model that allows for 14 400 possible arrangements of (1) in the asymmetric unit, making this structure one of the most complex structures in the Cambridge Structural Database to date. All disorders are exceptionally well resolved and exhaustive parameterizing affords a refinement model that is unique with respect to the detail of disorder refinement.