Metallocene-Appended Imidazoles Displaying Virtual Planar Chirality

( S )-1-(1-Alkylethyl)imidazoles 6a / b (alkyl = cyclohexyl, tert -butyl) containing a 2-(η 5 -cyclopentadienyl)(η 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 )-( p R ) 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.