Preparation and hydrogen bonding in ferrocenecarboxamides substituted with 2-hydroxyethyl groups at the amidenitrogen atoms

Abstract

The ferrocenecarboxamides, N-(2-hydroxyethyl)ferrocenecarboxamide (1a), N,N-bis(2-hydroxyethyl)ferrocenecarboxamide (1b), N,N′-bis(2-hydroxyethyl)ferrocene-1,1′-dicarboxamide (2a), and N,N,N′,N′-tetrakis(2-hydroxyethyl)ferrocene-1,1′-dicarboxamide (2b) were synthesized by amidation of the respective ferrocenecarboxylic acids, characterized by spectral methods including variable-temperature NMR spectroscopy, and their crystal structures were determined by single-crystal X-ray diffraction analysis. In the solid-state, the amides associate predominantly via two-centre O–H⋯O and N–H⋯O hydrogen bonds with a support from the softer C–H⋯O interactions. The supramolecular aggregation takes various forms, ranging from infinite one-dimensional hydrogen-bonded chains (1a) and ladder-like arrays (1b) to complicated three-dimensional networks (2a and 2b), and its complexity apparently increases with the number of the potential hydrogen bond donor and acceptor groups present in the molecule.