The class of “porcupine compounds”, includes the title cation 1, whose structure has been determined as the BPh4 salt. The analytically, mass‐spectrometrically and crystallographically detected interstitial C atom occupies the crystallographic inversion center in an octahedron composed of gold atoms: the structure is probably stabilized by AuċAu interactions. The periphery of tetraauriomethanes is apparently “aurophile” with respect to further LAu⊕ ions, so that the hypervalent complex cation [C(AuL)6]2⊕ is formed spontaneously. The supposedly uncentered octahedral cluster cations formulated previously as (AuL) 62⊕ were in fact probably indentical with the C‐centered species described here.

The first defined complex for oligo‐ and polymerization of ethylene which requires no co‐catalyst is the crystalline nickel complex (1). Its structure was established by X‐ray analysis. Dissolved in toluene, compound (1) reacts with ethylene (50 bar) at 50°C giving almost exclusively linear α‐olefins; linear polyethylene is formed under a different set of conditions.

η5-Cyclopentadienyl-stabilized metallacyclopentane and -cycloheptane derivatives of chromium have been isolated, and their chemical behavior lends support to a metallacyclic mechanism for the Cr-catalyzed selective trimerization of ethylene to 1-hexene. In the presence of MAO, the amino-substituted cyclopentadienyl−chromium derivatives show a remarkable activity for the catalytic polymerization of ethylene.

Cationic iridium(1) complexes of chiral phosphanodihydrooxazoles were uscd as catalysts for the enantioselective hydrogenation of prochiral N-alkyl and N-aryl imines. The complexes are air-stable crystalline solids that can be readily prepared and are easy to handle. The structures of two complexes were determined by X-ray analysis. For N-alkyl imines of acetophenone, enantiomeric excesses of up to 79% were obtained. Dialkyl ketimines and cyclic imines showed lower reactivity and selectivity. A remarkable dilution effect was observed for the hydrogenation of the N-phenyl imine of acetophenone: decreasing the substrate and catalyst concentration led to a signifi- Keywords