F-ELEMENT CROWN ETHER COMPLEXES .27. THE SYNTHESIS AND CRYSTAL-STRUCTURE OF [CE(NO3)3(OH2)(12-CROWN-4)].12-CROWN-4

A unique cerium nitrate complex, [Ce(NO3)3(OH2)(12-crown-4)]-12-crown-4, has been crystallized from the reaction of hydrated cerium nitrate and 12-crown-4. It crystallizes in the orthorhombic space group, Pnma, with (at -150°C)a = 22.901(5), b = 13.547(3), c = 8.422(1)Å, and Dx = 1.77 g cm-3 for Z = 4 formula units. A final R value of 0.048 was obtained utilizing 2059 unique observed [Fo ≥ 5σ(Fo)] reflections. The Ce atom resides on a crystallographic mirror plane and is 11-coordinate, coordinated to three bidentate nitrate groups, one water molecule and the four oxygens of one 12-crown-4 molecule. The water molecule hydrogen bonds a second 12-crown-4 unit. Both unique crown molecules and one of the nitrate anions are severely disordered. © 1990 Kluwer Academic Publishers.