Synthesis and crystallographic characterization of [Eu(C18H18N6)(OAc)(2)(+)][Cl-]center dot 7H(2)O, a ten-coordinate Eu(III) complex with a close-to-planar hexadentate C18H18N6 ligand: An interesting case of a structure withmultiple disorder problems

The title compound crystallizes in the centrosymmetric triclinic space grou p P (1) over bar (No. 2) with a=8.7080(18)Angstrom, b=9.2777(14)Angstrom, c =10.2707(22)Angstrom, alpha=77.762(14)degrees, beta=77.482(17)degrees, gamm a=84.735(15)degrees V=790.7(3)Angstrom(3) and Z=1. The structure was solved and refined to R=2.37% and wR = 3.19% for all 2073 independent reflections . The structure is disordered, with overlapping images of two enantiomeric [Eu(C18H18N6)(OAC)(2)(+)] ions surrounding an inversion center on which lie s a Eu(III) cation. These two images correspond to isomers with lambda lamb da and delta delta conformations of their N-CH2-CH2-N moieties, The ten-coo rdinate europium(III) cation has a staggered 2:6:2 coordination geometry, w ith six equatorial Eu-N bonds to the hexadentate macrocyclic ligand and two quasi-axial Eu-O bonds to each of the two bidentate acetate ligands. Furth er manifestations of disorder occur for the acetate ligands and for H2O/Cl- sites in the crystal lattice.