(Ferrocenylmethyl)trimethylammonium iodide (1), [C 14- H20FeN][I], Mr = 385.07, monoclinic, P2dc, a = 8.6236 (5), b = 13.5926 (10), c = 12.8623 (6) A, ~ = 102.792 (4)° , V = 1470.3 (2) A 3, Z = 4, T = 293K, F(000) = 760, Dx = 1.74 gcm -3, Mo Ks, A -- 0.71069 ,~, # = 3.08mm -l, R = 0.024 for 4075 observations [I > 30"(/)]. The [{(CsHs)Fe(CsH4)I-CH2N(CH3)3] + cation is involved in a three-dimensional network of C--H...I- interactions (both the cation and anion residing in general positions). The shortest C.-.I distances are 3.954 (2), 3.992 (2) and 4.009 (3) A. Hexa-Nmethylferrocene- 1,1'-diylbis(methylammonium iodide) (2), [C18H30FeN2].2[I], Mr = 584.10, monoclinic, C2/c, a = 27.1457(12), b -- 12.3446(6), c = 14.5295 (10) ,A,, /3 = 115.909 (4) °, V = 4379.5 (4) A, 3, Z = 8, T = 293 K, F(000) = 2264, Dx -- 1.772gcm -3, MoKa, A = 0.71069A, # = 3.48mm -I, R = 0.031 for 4482 observations [I > 30"(/)]. In (2), the [Fe{(CsHa)CH2-N(CH3)3}2] 2÷ cation (which has approximate twofold symmetry) and one of the anions reside in general positions. Another iodide resides on a twofold axis, while a third iodide lies on an inversion centre. A more extensive three-dimensional network of C--H---I- interactions is present in (2) than in (1) and involves all three of the iodide anions. The shortest C--.I- contacts are 3.733 (4) and 3.848 (4) A~ and involve the iodide which resides in a general position (all three iodides have C...I contacts < 4.1 A).