Synthesis, reactivity, electrochemical behaviour, and molecular structure of crown ether cyrhetrene complexes

Cyrhetrenyl crown ether complexes [(η5-C5H4CHN-M)Re(CO)3] (where M = 4-benzo-15-crown-5 (3a), 4-benzo-18-crown-6 (3b), 2-methyl-15-crown-5 (3c), or 2-methyl-18-crown-6 (3d)) were synthesised from cyrhetrenylcarboxaldehyde (1) and the corresponding crown ether amines 2a–d. All the complexes were characterised by IR spectroscopy, 1H and 13C NMR spectroscopies, and mass spectrometry. The stereochemistry for imine compounds 3a–d were determined using the 1H and 13C NMR spectroscopy data, which indicated that these complexes have the anti-(E) conformation. This was also confirmed by the X-ray crystal structures of 3b and 3c in the solid state. Additionally, the electrochemical behaviours of 1 and 3a–d were studied.