The tetrahydrofuran adduct of samarium diiodide, a reagent used extensively in organic synthesis as a unique one-electron reductant, crystallizes from THF as the seven-coordinate solvate SmI2(THF)(5), 1. Crystallization of this reagent in the presence of 1,2-dimethoxyethane (DME) generates related seven-coordinate mixed ether solvate derivatives SmI2(DME)(2)(THF), 2, and SmI2(DME)(THF)(3), 3. These solid state studies show that in the presence of excess oxygen donors like ethers, the SmI2 moiety prefers a seven-coordinate pentagonal bipyramidal geometry with iodide ligands in the axial positions. 1 crystallizes from THF at -35 degrees C in space group P2(1)/n with unit cell parameters at 163 K of a = 23.154(12) Angstrom, b = 26.033(6) Angstrom, c = 23.866(10) Angstrom, beta = 111.69(4)degrees, V = 13367(11) Angstrom(3), and Z = 16. 2 crystallizes from THF/DME at -35 degrees C in space group C2/c with unit cell parameters at 168 K of a = 13.0111-(14) Angstrom, b = 11.3727(10) Angstrom, c = 15.383(2) Angstrom, beta = 114.989(8)degrees, V = 2063.2(4) Angstrom(3), and Z = 4 for D-calcd = 2.113 g/cm(3). Least-squares refinement of the model based on 1826 reflections (F-0 > 3.0 sigma(F-0)) converged to a final R(F) = 4.0%. 3 crystallizes from THF/DME at -35 degrees C in space group P2(1)/c with unit cell parameters at 158 K of a = 17.177(2) Angstrom, b = 8.8869(8) Angstrom, c = 16.137(4) Angstrom, beta = 99.556(11)degrees, V = 2429.0(7) Angstrom(3), and Z = 4 for D-calcd = 1.943 g/cm(3). Least-squares refinement of the model based on 5971 reflections (F-0 > 3.0 sigma(F-0)) converged to a final R(F) = 4.4%. The Sm-I distances are 3.231(1) to 3.246(1) Angstrom in these structures and the Sm-O(ether) distances vary from 2.530(5) to 2.646(4) Angstrom.