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-1κS:2κN)-(μ-1κN:2κS)-thiocyanato-, and (μ-1κO:2κN)-(μ-1κN:2κO)-nitrito-bridged planar chiral dimers and bis(diphenylacetylene) insertion products have been elucidated by single-crystal X-ray analysis.