Anionenaktivierung, IV. Kristall‐ und Molekülstruktur des Adduktes von Malononitril mit 18‐Krone‐6 (1,4,7,10,13,16‐Hexaoxacyclooctadecan)

Abstract

Die Struktur des Adduktes 2 Malononitril · 18‐Krone‐6 wurde röntgenographisch bestimmt und bis zu einem R‐Faktor von 0.049 verfeinert. Die Verbindung kristallisiert in der Raumgruppe P21/c. Die Malononitrilmoleküle bilden über CH · · · ·O‐Wasserstoffbrücken mit dem Kronenether analog den bicyclischen Aminopolyethern einen dreidimensionalen Hohlraum von ca. 100 pm Durchmesser. Der Kronenether hat wie im KSCN‐Komplex annähernd D3d‐Symmetrie.

The Structure of a 2:1 Host Guest Complex between p-Nitroaniline and 18-Crown-6

“…[1,2]) and when hydrogen bonding to guest species [3][4][5][6]. This symmetry with exclusively ag±a units of alternating signs is also found in the structure of the present adduct ( Fig.…”

A 2:1 complex of 2,4-dinitroaniline and 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6)

“…18-Crown-6 normally adopts a conformation of approximate D3a symmetry both in cationic complexes (e.g. Dunitz, Dobler, Seller & Phizackerley, 1974;Nagano, 1979) and when hydrogen bonding to guest species (Nagano, Kobayashi & Sasaki, 1978;Goldberg, 1975;Kaufmann et al, 1977;Hilgenfeld & Saenger, 1981) including cationcoordinated water (Kn6chel, Kopf, Oehler & Rudolph, 1978b). With dihydrated uranyl nitrate (Bombieri, de Paoli & Immirzi, 1978) or benzenesulphonamide (Kn6chel et al, 1978a), however, this symmetry with exclusively anti-gauche-anti units of alternating signs is broken in favour of an elongated conformation g+g+aag-aag-ag-g-aag+aag+a which is related to that of the uncomplexed ether (Maverick, Seller, Schweizer & Dunitz, 1980).…”

A non-symmetric water complex of a tripod ligand: the structure of tris[(2-methyl-8-quinolyloxy)ethyl]amine dihydrate

“…Bond lengths and angles are given in Tables 2 and 3. Diseussion. Organic polar molecules or ions such as malononitrile, tetramethylenediammonium or thiourea can replace metal cations in host-guest complexes of cyclic crown ethers (Kaufmann, Knoechel, Kopf, Oehler & Rudolph, 1977;Goldberg, 1977) and also of linear oligoethers (Weber & Saenger, 1980b). Normally, water is only involved in linking ligands, as in the dimeric structure of a complex (Weber & Saenger, 1980a).…”