“Tail–Tail Dimerization” of Ferrocene Amino Acid Derivatives

Abstract

AbstractAcid anhydrides of N‐protected 1′‐aminoferrocene‐1‐carboxylic acid (Fca) have been prepared and spectroscopically characterized (protection group Boc, Fmoc, Ac; 4a–4c). The structure of the Boc‐derivative 4a has been determined by single‐crystal X‐ray crystallography. An intramolecular N–H···O hydrogen bond involving the carbamate units results in a ring structure containing the two ferrocene units, the anhydride moiety, and the hydrogen bond. In the crystal, the individual molecules are connected by intermolecular N–H···O hydrogen bonds of the carbamate unit. Experimental and theoretical studies suggest that the ring motif is also a dominant species in solution. Electronic communication across the anhydride moiety is found to be very weak as judged from electrochemical, spectroscopic, and theoretical experiments.