Röntgenstrukturanalysen von Chiralen Ionophoren: NH4NCS-Komplex von 9,9′-Spirobifluoren-22-Krone-5

X-ray Structure Analyses of Chiral Ionophores: The NH₄NCS Complex of 9,9′-Spirobifluorene-22-crown-5 In the crystalline NH₄NCS complex of 9,9′-spirobifluorene-22-crown-5 ( 1 ) the NH ion sits in the centre of the polyether ring, with distances of 2.92–3.15 Å to the five O-atoms and shows at least twofold orientational disorder. In one orientation, three H-atoms point toward O-atoms and the fourth to the N-atom of the anion situated 2.78 Å above the polyether ring. In another, only two H-bonds are formed. The mean planes of the two fluorene parts of the molecule are perpendicular to each other. Crystals of 2,2′-bis (hydroxymethyl)-9,9′-spirobifluorene ( 2 ), an intermediate for the synthesis of 1 , contain occluded benzene, which cannot be removed under vacuum. X-ray analysis shows that the benzene molecule does not interact with the spirobifluorene in a specific way but merely occupies cages in the crystal packing.