Chiral ortho-Palladated and -Platinated Arylphosphite Complexes

Abstract

A series of chiral bis-phosphite complexes 8−11 [MCl2(L)2] (M = Pd or Pt) and ortho-metalated, C,P-chelate-bonded monophosphite complexes 12−14 [M(κ2-L)(μ-Cl)]2 have been prepared by reacting enantiopure (R)-BINOL-derived arylphosphite ligands L with readily accessible palladium or platinum precursors under appropriate conditions. The reactivity of complexes 12−14 containing the chiral C,P-bidentate-bonded arylphosphite ligands toward various monodentate and bidentate ligands was studied. It was found that the ortho-palladated complexes 12 and 13 do not cleanly react with triphenylphosphine in dichloromethane, whereas ortho-platinated complex 14 smoothly reacts with typical monodentate or bidentate ligands such as pyridine, triphenylphosphine, tricyclohexylphosphine, triphenylphosphite, and [1,2-bis(diphenylphosphino)ethane] to generate the corresponding monomeric chiral ortho-platinated complexes 18−23 in good to excellent yields. Besides the full characterization of all novel complexes by NMR techniques and mass spectroscopy as well as elemental analysis, the structures of complexes 10, 18, 19, and 23 in the solid state (X-ray crystal structure determination) were established. The purpose and potential of employing the ortho-platinated complex 14 either as a resolution reagent or as a chiral NMR shift reagent were studied. Both enantiomers of racemic α-methylbenzylamine could be resolved with promising yields