The crystal structures of (NH 3 (CH 2 ) 6 NH 3 )SnI 4 and (NH 3 (CH 2 ) 8 NH 3 )SnI 4 are "Ruddlesden-Popper" perovskite derivatives, which consist of single-octahedral layers as a "two-dimensional" inorganic framework separated by [NH 3 (CH 2 ) n NH 3 ] 2+ (where n = 6, 8) cations. In contrast, the formula, (NH 3 (CH 2 ) 7 NH 3 ) 2 Sn 3 I 10 can be re-written to highlight the structure in the chemical formula, (NH 3 (CH 2 ) 7 NH 3 )(Sn 0.5I )I 4 , as the crystal structure contains the same layers of corner-linked octahedra, but with an additional [Sn(II)I 5 ] square pyramid in between the layers to provide a three-dimensional connectivity of the inorganic polyhedra. As such, the titled compound has more in common with the so-called "Dion-Jacobson" layered perovskites in which the halides facing the organic layer are in registry. Analysis of the structures from (NH 3 (CH 2 ) n NH 3 )SnI 4 and the titled compound reveal the trend presented in Figure . For n = 7, the gap distance lies above the linear trend exhibited by the others, consistent with the expected expansion from going from a NaCl-like packing to CsCl-like packing of the A-X sites. As such, we expect these geometric trends to be useful in predicting the formation of other new compounds with related structures.