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

Abstract

Cyrhetrenyl crown ether complexes [(eta(5)-C5H4CH=N-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, H-1 and C-13 NMR spectroscopies, and mass spectrometry. The stereochemistry for imine compounds 3a-d were determined using the H-1 and C-13 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.