Coordination Chemistry of New Chiral P,N Ferrocenyl Ligands with Half-Sandwich Ruthenium(II), Rhodium(III), and Iridium(III) Complexes

Abstract

The new half-sandwich ruthenium(II), rhodium(III), and iridium(III) complexes (p-cymene)RuCl2L and Cp*MCl2L (M = Rh, Ir), where L is a planar chiral ferrocenyl tosylamine-phosphine ligand {1,2-(TosNRCH2)(PPh2)C5H3}FeCp (R = H, Me) coordinated in a monodentate fashion (κ1P), have been synthesized and fully characterized both in solution (multinuclear NMR, mass spectrometry) and in the solid state (X-ray analysis on single crystals). Intra- and intermolecular N–H···Cl bonds were observed. Variable-temperature NMR shows an equilibrium between different structures, which have been discussed with the help of DFT calculations. Addition of triethylamine to the complexes with R = H allows removing the tosylamide acidic hydrogen, giving rise to a ferrocenyl amidophosphine ligand coordinated in a bidentate fashion (κ2P,N). All complexes have been fully characterized by multinuclear NMR and mass spectrometry. The structure of the iridium complex, determined by X-ray diffraction, shows a planar nitrogen atom and a stable metal-centered chirality. Only the most stable diastereoisomer, according to DFT calculations, has been observed. A number of these complexes were assessed in the catalytic transfer hydrogenation and asymmetric transfer hydrogenation of acetophenone.