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

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.