Cover Picture (Angew. Chem. Int. Ed. Engl. 2/1991)

The cover picture shows triisopropylamine, which according to electron diffusion studies in the gas phase contains a planar NC 3 skeleton and thus an electron pair in a nitrogen p‐orbital. The graphics illustrate the facts: The molecular skeleton represents the global minimum of a MNDO energy hypersurface and agrees satisfactorily with the experimentally determined structure. In addition the van der Waals radii of the isopropyl hydrogen atoms and methyl groups are drawn and shaded. To illustrate the charge density, the electron pair on the nitrogen atom, which stems from an ab initio SCF calculation, is drawn in red. The wave function contours are Slater 2p atomic orbitals. Triisopropylamine is synthesized in a four‐step process and has exceptional properties: it has a first vertical ionization energy of only 7.18 eV, it may be reversibly oxidized by cyclic voltammetry, and the ESR signal pattern of its radical cation consists of only the 1 : 1 : 1‐ 14 N triplet. The “flattened nitrogen pyramid” structure, forced upon the molecule by steric crowding and proven first for a trialkylamine, was inferred from these facts and from quantum mechanical calculations. It approximates a double minimum potential with low inversion barrier. Further details of this simple but fascinating compound are reported by H. Bock, I. Goebel, Z. Havlas, S. Liedle and H. Oberhammer on page 187.