Resolutions Involving Metal Complexation. Resolution of (α)-1-Amino-2-(Methylphenylarsino)Ethane and its Phosphorus Analog. Stereochemistry and Stability of Square-Planar Bis(Bidentate) Complexes of Bivalent Palladium and Platinum

Abstract

The asymmetric bidentates (±)-l-amino-2-(methylphenylarsino)ethane and its phosphorus analogue have been resolved by fractional crystallization of internally diastereoisomeric palladium(II) complexes containing optically active ortho-metalated dimethyl(l-ethyl-a-naphthyl)amine. Optically pure enantiomers of both ligands were obtained from the separated diastereoisomers in stereospecific displacements as high-boiling air-sensitive oils with [a]D(CH2Cl2) ±13° (arsine) and ±16° (phosphine). Absolute configurations have been assigned to the enantiomers by a 'H NMR method involving a comparison of the spectra of the diastereoisomeric intermediates with others of known structure. The ligands form bis(bidentate) derivatives of palladium(II) and platinum(II) in which like donor atoms are cis to one another. The arsine complexes of both metals undergo facile ligand redistribution under ambient conditions, but the phosphine compounds are stable in this respect in the absence of free ligand. Indeed, condensation reactions take place between the platinum-arsine complexes and acetone, giving cations containing novel quadridentate ligands: these are the first examples of reactions of this type on platinum(II). Show more