Electron Donor-Acceptor Properties of Substituted Pyridine Ligands on Fac-Tricarbonylrhenium(i) Systems

A series of 4-substituted pyridines were combined with Re(CO)(5)Cl to prepare fac-tricarbonylchlorobis( ligand) rhenium(I) complexes. The Re(I) complexes were characterized by H-1 and C-13 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. (C) 2016 Elsevier B.V. All rights reserved.