Developments and properties of novel chiral cyclopalladated complexes of arsine or phosphine ligands

Abstract

A series of five novel chiral, cyclopalladated complexes (and their derivatives) derived from either the affiliated arsine or phosphine ligands have been prepared in the optically a?? active and racemic states. The first three of these five-membered ortho-palladated complexes were derived from the chiral ligands, 1-(1-naphthyl)ethyldiphenylphosphine, 1-(1-naphthyl)ethyldiphenylarsine and 1-(2a??, 5a??-dimethylphenyl)ethyldiphenylphosphine. The next two ortho-palladated complexes of this series were obtained from the prochiral ligands, (diphenylmethyl)diphenylphosphine and (diphenylmethyl)di-tert-butylphosphine.Their preparations and the various properties of these new chiral cyclopalladated complexes are discussed. These properties include the fluxional behavior of the chloro-bridged dimeric complexes, the conformational properties of the five-membered palladacycles observed from NMR spectroscopic studies, the stabilities of the Pd-C bonds as well as the stereoelectronic behavior of these palladacycle complexes. Additionally, the unusual coordination properties of the last ligand, (diphenylmethyl)di-tert-butylphosphine and the attempts made to prepare its corresponding phosphapalladacycle in the optically active state by asymmetric cyclopalladation are also mentioned.