Hydrogen-bond-assisted, concentration-dependent molecular dimerization of ferrocenyl hydantoins

The synthesis and characterization of the ferrocenyl methylhydantoin 5-ferrocenyl-5-methylimidazolidine-2,4-dione, efficiently prepared through a Bucherer-Bergs reaction, and its derivatives carrying tert-butoxycarbonyl (Boc) protecting groups, namely 1,3-bis(tert-butoxycarbonyl)-5-ferrocenyl-S-methylirnidazolidine-2,4-dione and 1-(tert-butoxycarbonyl)-5-ferrocenyl-5-methylimidazolidine-2,4-dione, are reported. X-ray diffraction and ESI-mass spectrometry analyses of the ferrocenyl methylhydantoin revealed the presence of C=O center dot center dot center dot H-N intermolecularly hydrogen-bonded dimers. The mono-Boc derivative formed a hydrogen-bonded dimer in solution, as confirmed by H-1 NMR, FT-IR, and cyclic voltammetry experiments at different concentrations in CDCl3 or CHCl3.