Cyclic Ether Induced Asymmetric Cyclopalladation:  Synthesis and Structural Characterization of Enantiopure Bis(μ-acetato)-Bridged Dimers of Planar Chiral Cyclopalladated Ferrocenylimines and Their Derivatives

Enantiopure bis(μ-acetato)-bridged planar chiral cyclopalladated products (R = H, Me) have been obtained by asymmetric cyclopalladation of the corresponding chiral ferrocenylimines with palladium(II) acetate and sodium acetate in methanol at room temperature with a high level of diastereoselectivity (product ratio syn -(+)-( R p, R, R, R p ): syn -(−)-( S p, R, R, S p ) ≈ syn -(−)-( S p, S, S, S p ): syn -(+)-( R p, S, S, R p ) ≈ 9:1). One or both acetato groups can be readily substituted by other anionic ligands to yield novel mixed-bridge or bis(μ-anion)-bridged planar chiral dimers of ferrocene derivatives. The first cis -type syn -( R p, S p ) cyclopalladated dimer of ferrocenylimine has been obtained. The diphenylacetylene insertion reaction of a variety of anion-bridged planar chiral dimeric cyclopalladated derivatives of ferrocene has also been investigated. The absolute configurations of bis(μ-acetato)-, bis(μ-halogeno)-, (μ-1κ S:2κ N )-(μ-1κ N:2κ S )-thiocyanato-, and (μ-1κ O:2κ N )-(μ-1κ N:2κ O )-nitrito-bridged planar chiral dimers and bis(diphenylacetylene) insertion products have been elucidated by single-crystal X-ray analysis.