CRYSTAL AND MOLECULAR-STRUCTURE OF A CRYPTATE COMPLEX OF SAMARIUM - C18H36O6N2SM2(NO3)6.H2O

A compound made by reacting Sm(NO3)3 with the cryptand designated [2.2.2] was analyzed by single-crystal X-ray diffraction to determine its composition, Cl8H36O6N2Sm2(NO3)6 H2O, and its molecular structure. The triclinic unit cell has a = 14.815 (3) Å,b = 8.813 (1) Å, c = 13.253 (3) Å, α = 91.51 (2)°, β = 92.48 (2)°, and γ = 86.73 (2)°; the space group is P1 and Z = 2. The structure was determined by the heavy-atom method and refined by least squares. Positions and anisotropic thermal parameters of the 53 independent nonhydrogen atoms of the asymmetric unit were adjusted until the agreement factor, RF, reached 0.038 for 6941 observations. The crystal contains two complex ions: (Sm[2.2.2]NO3)2+ and [Sm(NO3)5-H2O]2-. In the complex cation the Sm3+ ion is enclosed in the bicyclic ligand and is bonded to its six O atoms and two N atoms as well as to a bidentate NO3- ion inserted between strands of the ligand. Considerable distortion of the ligand from its conformation in the uncomplexed state is observed. The complex anion has five bidentate NO3-ions and a water molecule surrounding a Sm3+ ion. There are no especially close contacts between ions other than for some weak hydrogen bonds. © 1979, American Chemical Society. All rights reserved.