Electron donor-acceptor properties of substituted pyridine ligands on fac-tricarbonylrhenium(I) systems

• Five new fac-tricarbonylchlorobis(ligand)rhenium(I) complexes were prepared.
• Back bonding differences caused by pyridine substituents are observed by FTIR.
• Back bonding differences cannot be seen in the single crystal X-ray structures.
• These complexes are air-stable, diamagnetic, and easily synthesized.

A series of 4-substituted pyridines were combined with Re(CO)5Cl to prepare fac-tricarbonylchlorobis(ligand)rhenium(I) complexes. The Re(I) complexes were characterized by 1H and 13C NMR spectroscopy, FTIR spectroscopy, HRMS, and in the case of L = 4-(trifluoromethyl)pyridine, 4-bromopyridine, 4-picoline, and 4-methoxypyridine, single crystal X-ray diffraction studies. In the carbonyl region of the FTIR spectra for these complexes, the three observed stretches shifted to higher energy as the substituent on the pyridine became more electron withdrawing.

A series of 4-substituted pyridines were combined with Re(CO)5Cl to prepare fac-tricarbonylchlorobis(ligand)rhenium(I) complexes. Electronic effects of the substituents were observed in the carbonyl region of the FTIR spectra for these complexes, but not in the X-ray structures.Figure optionsDownload as PowerPoint slide