(I) and (18-crown-6)(nitrato-O,O')potassium(0.91)silver(0.09) (II). Their isomorphic orthorhombic crystals (space
group P212121, Z = 4) are studied by X-ray diffraction analysis. Structure I (a = 8.553 Å, b = 11.967 Å, c =
17.871 Å) and structure II (a = 8.540 Å, b = 11.956 Å, c = 17.867 Å) are solved by a direct method and refined
by the full-matrix least-squares method in the anisotropic approximation to R = 0.044 (I) and 0.055 (II) for all
2385 (I) and 2379 (II) measured independent reflections. Complex molecules [K(NO3)(18-crown-6)] in struc-
ture I and [K0.91Ag0.09(NO3)(18-crown-6)] in compound II are of the host–guest type and rather similar in
structure. Their 18-crown-6 and
ligands are disordered over two orientations. The K+ cation in complex I and the mixed cation (K0.91Ag0.09)+ in complex II reside in the cavity of the disordered 18-crown-6 ligand and
is coordinated by its six O atoms and by two disordered O atoms of the
ligand. The coordination poly-hedron (CN = 8) of the K+ cation in complex I and that of (K0.91Ag0.09)+ cation in complex II is a distorted hex-
agonal pyramid with a base of six O atoms of the 18-crown-6 ligand and a split vertex at two O atoms of the
ligand.