We synthesize single crystals of a new 2,5-dimethylanilinium tin iodide organic-inorganic hybrid compound and 2,5-dimethylanilinium triiodide. Single-crystal X-ray diffraction reveals that the hybrid grows as a unique rhombohedral structure consisting of one-dimensional chains of SnI6-octahedra that share corners and edges to build up a ribbon along the  direction. Notably, we find that hypophosphorous acid, H3PO2, is of central importance to the formation of this hybrid. In the absence of H3PO2, we synthesize 2,5-dimethylanilinium triiodide from the same starting compounds. We investigate the synthesis routes that drive the growth of these two compounds with distinct crystal structures, appearance and properties. Pulse-radiolysis time-resolved microwave conductivity measurements and density functional theory calculations reveal that both compounds have low charge carrier mobilities and very long lifetimes, consistent with their one-dimensional structural characteristics. Our findings give a better understanding of the relation between synthesis, crystal structures and charge carrier mobilities.