Formation of intramolecular hydrogen bonds in heterodisubstituted ferrocene diamides with a secondary and a tertiary amido group: X-ray structure of 1′-(N′-butyl-carbamoyl)-morpholino ferrocenecarboxamide

Various unsymmetrically substituted ferrocene 1,1′-diamides have been synthesized via homogeneous catalytic carbonylation starting from 1,1′-diiodoferrocene. The unique features observed in the 1H NMR and IR spectra of the compounds bearing a secondary and a tertiary amido group are explained by the formation of an internal hydrogen bond between the substituents. Addition of chloride ions (as a tetrabutylammonium salt) into the solutions of these compounds results in spectroscopic changes due to the formation of intermolecular hydrogen bonds between the ferrocene diamide and the anion. The solid state structure of 1′-(N′-butyl-carbamoyl)-morpholino ferrocenecarboxamide (1a) has also been determined by X-ray crystallography. A strong intramolecular H-bond between the NH group of the N′-butyl-carbamoyl moiety and the CO of the tertiary amido group was observed.

Unsymmetrical ferrocene 1,1′-diamides with one secondary and one tertiary amido group form intramolecular hydrogen bonds both in the solid state and in solution. The structure of (BuNHCOC5H4)Fe(C5H4CON(CH2CH2)2O) (1a) is determined by X-ray crystallography, as well as solution-phase 1H NMR and infrared spectroscopy. The hydrogen bond can be cleaved upon addition of chloride ions.Figure optionsDownload as PowerPoint slide