Isolation and absolute configuration of diastereomeric di-μ-chloro-bridged dimers of a planar chiral cyclopalladated ferrocenylimine

Reaction of acetylferrocene (1) with (-)-(S)-1-amino-2-(methoxymethyl)pyrrolidine (-)-(S)-2 in dry benzene gave new chiral ferrocenylimine (+)-(S)-FcC(CH3)=NNCH2CH2CHCH2OCH3 [(+)-(S)-3]. Asymmetric cyclopalladation of (+)-(S)-3 with sodium tetrachloropalladate(II) and sodium acetate trihydrate in methanol at room temperature gave a mixture of diasteromeric cyclopalladated products [Pd{(eta(5)-C5H3C(CH3)=NNCH2CH2CHCH2OCH3)Fe(eta 5-C5H5)}(mu- Cl)](2) [syn-(+)-(R-p,S,S,R-p)-4, anti-(-)-(R-p,S,S,S-p)-4 and syn-(-)-(S-p,S,S,S-p)-4] in ca. 67% total yield with a high level of diastereoselectivity. The three enantiopure compounds (product ratio 8:1:1) were isolated from the mixture through column-layer chromatography and their structural relationship elucidated by single-crystal X-ray analysis. (C) 1998 Elsevier Science Ltd. All rights reserved.