Compounds of the general formula Cu/sub m/I/sub m/(PR/sub 3/)/sub n/ . xSO/sub 2/, where PR/sub 3/ = PPh/sub 3/, PPh/sub 2/Me, PBzl/sub 3/, and PCy/sub 3/ (Bzl = benzyl; Cy = cyclohexyl), are formed by direct reaction of SO/sub 2/ with organophosphine copper (I) iodide complexes. The nature of the reaction solutions and isolated products has been elucidated by spectroscopic, tensimetric, and x-ray diffraction methods. Sulfur dioxide complexation occurs only at the coordinated halogen, even when three-coordinate copper (I) apparently is present in the complex. The strength of interaction is a strong function of both the specific phosphine and stoichiometry, and the bright yellow to orange crystalline complexes have SO/sub 2/ dissociation pressures of 2 to 70 Torr at ambient temperature. The crystal structure analysis of Cu/sub 2/I/sub 2/(PPh/sub 2/Me)/sub 4/ . SO/sub 2/ reveals a dimeric, di-..mu..-iodo-bridged structure involving pseudotetrahedral copper atoms and an SO/sub 2/ group bound weakly as a Lewis acid to one of the bridging iodides (I--S = 3.407 (5) A and I--S--O = 98.1 (6), 114.5 (8)/sup 0/). Additionally, we report the structure of the compound Cu/sub 2/I/sub 2/(PPh/sub 3/)/sub 3/ and its interaction with sulfur dioxide. X-ray structure determination reveals a dinuclear unit similarmore » to that found in Cu/sub 2/Cl/sub 2/(PPh/sub 3/)/sub 3/ with ..mu..-iodide bridges and both three-coordinate copper and four-coordinate copper. Pertinent crystallographic data are as follows: Cu/sub 2/I/sub 2/(PPh/sub 3/)/sub 3/, space group P2/sub 1/, a = 11.763 (4) A, b = 20.682 (4) A, c = 10.527 (3) A, ..beta.. = 105.66 (2)/sup 0/, Z = 2, R = 0.047 for 4139 diffractometric reflections (with I greater than or equal to 3sigma(I) and 2theta less than or equal to 60/sup 0/); Cu/sub 2/I/sub 2/(PPh/sub 2/Me)/sub 4/SO/sub 2/, space group P anti l, a = 20.02 (2) A, b = 12.062 (6) A, c = 14.898 (7) A, ..cap alpha.. = 116.30 (3)/sup 0/, ..beta.. = 68.44 (3)/sup 0/, ..gamma.. = 124.89 (2)/sup 0/, Z = 2, R = 0.052 for 7112 diffractometric reflections (with I greater than or equal to 3sigma(I) and 2sigma less than or equal to 50/sup 0/).« less