Trialkylation of 1-amino-1-carba-closo-dodecaborane with 1-bromo-3,3-bis(2-bromoethyl)octane affords 1-(4-pentylquinuclidin-1-yl)-1-carba-closo-dodecaborane in 29% yield which can then be iodinated to form title compound 1 in 40% yield. The molecular and crystal structure of 1 has been determined by X-ray crystallography [C13H33B11IN, monoclinic P21/c: a = 10.3405(2) Å, b = 16.4404(1) Å, c = 12.7223(2) Å, β = 100.156(1)°, Z = 4]. The structural features of 1 are compared with those in analogous compounds. The B-I bond length (2.196(6) Å) is an intermediate value between those found in neutral iodocarboranes and charged B12H11I(-2). NMR data is correlated with the structure of 1 and the additivity of NR3 and halogen substituent effects is tested.