Metallocene-appended imidazoles displaying virtual planar chirality

(S)-1-(1-Alkylethyl(imidazoles 6a/b (alkyl cyclohexyl, tert-butyl) containing a 2-(eta (5)-cyclopentadienyl)(eta (4)-tetraphenylcyclobutadiene)cobalt substituent are readily synthesized. The effect of the bulky metallocene is to place the imidazoles in. an environment of virtual planar chirality as revealed by X-ray crystallography (of 6a), NOE difference NMR spectroscopy, and also their highly diastereoselective reactions with Pd(OAc)(2) resulting in new palladacycles 7a/b with (S)-(pR) configurations. The ability of the imidazole complexes to act as nucleophilic catalysts was investigated, weak activity being found for the promotion of the reaction between ethanol and dimethylchlorophosphate.