Rhenium Complexes of Ligands Based on Stilbene - Synthesis, Characterization, Reactivity, and Conformational Analysis

The imine ligand L-1 was prepared by the reaction of 4-amino-4-(dimethylamino)stilbene and 2-pyridinecarbaldehyde. The amine ligand L-2 was obtained in good yield by the reduction of L-1 with NaBH4. The complexes [ReX(CO)(3)(L-n)] (1a: X = Cl, n = 1; 1b: X = Br, n = 1; 2a: X = Cl, n = 2; 2b: X = Br, n = 2) were prepared through the reactions of equimolar solutions of the corresponding ligand and [ReX(CO)(3)(CH3CN)(2)]. The complexes were characterized spectroscopically, and the structures of 1a and 1b were established by X-ray diffraction. A configurational and conformational study of the amine complex 2b in dimethyl sulfoxide (DMSO) solution was performed through molecular modeling and with the experimental NMR spectroscopy data. The transformations of 2a and 2b into 1a and 1b, respectively, were also monitored by UV/Vis and NMR spectroscopy.