The structures of the nitric oxide and dinitrogen tetroxide sorption complexes of dehydrated fully Cd2+- exchanged zeolite X (FAU) have been determined using single-crystal X-ray diffraction in the cubic space group Fd (3) over barm at 21(1) degrees C. Ion exchange was accomplished by allowing an aqueous stream 0.05 M in Cd2+ to flow past each crystal for 5 days. Each crystal was then dehydrated at 500 degrees C and 2 x 10(-6) Torr for 2 days, followed by exposure to 100 Torr of zeolitically dry NO or NO2/N2O4 gas. The structures were determined in these atmospheres. The unit cell constants at 21(1) degrees C are 24.877(2) angstrom for the dark-yellow NO complex, vertical bar Cd-46(NO)(16)vertical bar[Si100Al92O384]-FAU, and 24.735(2) for the black N2O4 complex, vertical bar Cd-46(N2O4)(25.5)vertical bar[Si100Al92O384]-FAU. The structure of the NO complex was refined to R-1 = 0.072 and wR(2) = 0.134. In this structure, Cd2+ ions occupy four crystallographic sites. Fifteen Cd2+ ions occupy site I (at the centers of the double 6-rings (D6Rs)), and one occupies site I' (in the sodalite cavity opposite a D6R). The remaining 30 Cd2+ ions occupy two different sites II (near 6-rings in the supercages): 16 coordinate to nitric oxide molecules and 14 do not. Sixteen NO molecules lie in the supercage where each interacts weakly with a Cd2+ ion: Cd-N = 2.57(22) angstrom. The observed N-O bond distance is 1.28(25) angstrom and Cd-N-O is 118(10)degrees. The structure of the N204 complex was refined to R-1 = 0.084 and wR(2) = 0.216. In this structure, Cd2+ ions occupy only three crystallographic sites. The 16 D6Rs per unit cell are filled with 11.5 Cd2+ ions at site 1 and 9 Cd2+ ions at site I': 11.5 + 9/2 = 16. The remaining 25.5 Cd2+ ions occupy site II where each coordinates at 2.43(8) angstrom to a nitrogen atom of a N204 molecule. At the coordinating nitrogen atom, O-N-O is 147(10)degrees and the N-O bond lengths are 1.07(9) and 1.23(10) At the second nitrogen atom, O-N-O is 140(10)degrees, and the N-O bond lengths are 1.03(13) and 1.42(12) The imprecisely determined N-N bond length, 2.74(17) angstrom, appears to be very much lengthened by coordination to Cd2+. The Cd-N-N angle is 144(10)degrees. This appears to be the first crystallographic report of the coordination of N2O4 to a cation.