Synchrotron X-ray diffraction data measured on a room temperature polycrystalline powder sample of 3 carried out at beamline I11 at Diamond Light Source could be indexed completely by the P2/n (2 × 6 × 4) supercell, with no peaks unaccounted for. Rietveld refinement using the model derived from SCXD data gave quantitative agreement [ESI Section 2.3; Figs. ]. Notably, excluding the MeNH 3 cations from the model significantly degraded the quality of fit (R wp increased from 2.97 to 3.59).