Synthesis, n.m.r. spectra, and structure of macrocyclic compounds containing the ferrocene unit

Abstract

The condensation of 1,1′-bis(chlorocarbonyl)ferrocene with diaza-18-crown-6 gives 1,1′-(1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane-7,16-diyldicarbonyl)ferrocene (5) together with its dimer 1,1″: 1′,1‴-bis-(1,4,10,13-tetraoxa-7,16-diazacyclo-octadecane-7,16-diyldicarbonyl) bisferrocene (6) and the separation and isolation of these compounds are described. High resolution ¹H and ¹³C n.m.r. spectra using homo- and hetero-nuclear decoupling techniques allow a complete assignment of the spectral data for (5) and (6) and lead to a proposal of a structure for (5) involving a trans-disposition of the amide carbonyl groups. Variable-temperature n.m.r. data on (6) reveal two distinct dynamic processes within the molecule involving rotation about the ferrocene-carbonyl bond (ΔG^‡= 50 kJ mol^–1, T_c=–10 °C) and rotation about the N–CO bond (ΔG^‡= 67 kJ mol^–1, T_c=+60 °C). The preparation, ¹H and ¹³C n.m.r. data of monocyclic compounds containing the ferrocene unit (13a–c), (14) and (15) are also described and the details of the synthesis of an ¹⁵N-labelled analogue of (13c), the macrocycle (16), are reported.