Iridium(I) homobinuclear complexes containing salen-type ligands as bridge

Abstract

New binuclear iridium(I) complexes with general formula [Ir2(η4-cod)2(μ-SB)] (1–12) derived from the reactions of tetradentate Schiff bases ligands [N,N′-ethylenebis(5-R-salicylideneimine)] (5,5′-R-salenH2), [N,N′-1,3-propylenebis(5-R-salicylideneimine)] (5,5′-R-salpenH2), and [N,N′-o-phenylenebis(5-R-salicylideneimine)] (5,5′-R-salphenH2) (R = H, MeO, Cl, NO2) with [Ir(cod)(μ-Cl)]2 were synthesized. The homobinuclear nature of this iridium complexes was supported by elemental analysis, FAB-Mass and 1H NMR spectrometry. Full characterization was accomplished by IR spectroscopy, 13C NMR and bidimensional NMR experiments (COSY, HSQC, HMBC and NOESY). In addition, iridium complex [(Ir(η4-cod)2(μ-5,5′-MeO-salen)] (2) was characterized by X-ray crystallography, showing that ethylene bridge is a s-trans conformation, and that the Schiff base ligand act as a bridging N,O-bidentate ligand toward two iridium atoms, and 1,5-cyclooctadiene (cod) ligand complete the coordination sphere of metal center. The effect of the substituent groups on salicylaldiminate fragments has been studied by 13C{1H} NMR shift and Hammett sigma correlations for each series of complexes.