Cationic rhodium(I) complexes containing 4,4′-disubstituted 2,2′-bipyridines: A systematic variation on electron density over the metal centre

A series of [Rh(COD)(X2-bipy)]BF4 complexes (COD = 1,5-cyclooctadiene; X2-bipy = 4,4′-disubstituted 2,2′-bipyridines; X = OCH3, CH3, H, Cl or NO2) has been prepared from [Rh(COD)Cl]2. The complexes for X = OCH3, Cl and NO2 have not been described previously in the literature. All complexes have been characterised by elemental analysis, IR, 1H NMR and UV–Vis spectrometry. This series of complexes presents a wide variation on electron density over the metal centre with virtually no variation on its steric environment which discloses interesting possibilities for catalytic and electro-catalytic studies. A preliminary evaluation of these complexes on the hydroformylation of camphene and β-pinene showed that under the rather drastic conditions employed the complexes acted as a precursor for [Rh(CO)3H], which accounts for most of the catalytic activity.

Graphical abstractA series of cationic rhodium(I) complexes containing 4,4′-disubstituted 2,2′-bipyridines were synthesized. The electron density over the metal varies largely with X with virtually no change on its steric environment. The complexes were evaluated on the hydroformylation of terpenes.Figure optionsDownload full-size imageDownload as PowerPoint slide