The naphthylamine palladium(II) template induced E-Z isomerism of exocyclic vinyl group in five-membered P-N chelates: Detailed spectroscopic studies

Abstract

The exocyclic C=C bond E-Z isomerism of chelating Ph2PC(=CHPh)- CH=NAr in organopalladium complexes containing orthometallated [(S)-1-(dimethylamino)ethyl]naphthalene is reported. In dilute solutions of non-coordinating CH2Cl2 or CHCl3, all the original E-isomers, in which the =CHPh phenyl rings are located trans to PPh2 moieties were partly converted to their Z-isomers. The isomerism was found to be dependent on temperature, concentration and solvent. At higher temperature, the Z-isomers were transformed completely back to their original E-isomers. Removal of the chiral auxiliaries of the E-Z mixtures by concentrated HCl, gave only the dichloro complexes of the E-isomers. The E-Z isomerization processes were well established by detailed spectroscopic studies, including 31P NMR, 1H NMR and 2D 1H-1H ROESY NMR studies. It is noteworthy that the dichloro complexes and free P-N ligands did not show such isomerization processes, indicating that the isomerization processes were triggered by the orthopalladated naphthylamine moiety. © 2004 Elsevier B.V. All rights reserved.