Angewandte Chemie International Edition

Cover image for Vol. 56 Issue 31

Editor: Peter Gölitz, Deputy Editors: Neville Compton, Haymo Ross

Online ISSN: 1521-3773

Associated Title(s): Angewandte Chemie, Chemistry - A European Journal, Chemistry – An Asian Journal, ChemistryOpen, ChemPhotoChem, ChemPlusChem, Zeitschrift für Chemie

Cover Picture (Angew. Chem. Int. Ed. Engl. 3/1990)

29_03/1990The cover picture shows the structure of an almost T-symmetrical chelate(4–)-ion, whose core is a tetrahedron of four cobalt(II) ions (dark blue) (viewed along the crystallographic C2 axis). The four cobalt(II) ions are each coupled via the six tetrahedron edges by a double bidentate chelate(2–)bracket (green) such that each of the four metal ions is surrounded octahedrally by six oxygen atoms (red). The complex chelate(4–)ion is formed by spontaneous self-assembly, a very common structural principle in nature. The tetramethyl-2,3-dioxobutane-1,1,4,4-tetracarboxylato(2–) is first formed by template coupling of two malonic ester monoanions with oxalyl chloride. Multinuclear metal chelate complexes are of considerable interest as model substances in the elucidation of the structure and mode of action of the active centers in metalloproteins. Further details of the preparation and structure of tetranuclear MNII-, CoII- and NiII- chelate(4–)ions with idealized T-symmetry are reported by R. W. Saalfrank et al. on p. 311 ff.

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