Cr. Landis et al., Synthesis and characterization of a chiral, aza-15-crown-5-functionalized ferrocenyldiphosphine ligand for asymmetric catalysis, ORGANOMETAL, 19(6), 2000, pp. 994-1002
A chiral ferrocenyldiphosphine ligand that is functionalized with an aza cr
own ether, (S)1-[(R)-1',2-bis(diphenylphosphino)ferrocenyl]ethyl-1-aza-2,3-
benzo-15-crown-5 (1), has been synthesized. Both the resolved and racemic l
igands react rapidly with Pt(II) precursors to form stable metal-ligand add
ucts; the complexes PtMeI(rac-1) and PtMe2(rac-1) have been characterized c
rystallographically. Reaction of rac-1 with [Rh(NBD)(2)]OTf yields [Rh(NBD)
(rac-1)]OTf. The three-dimensional solution structure of [Rh(NBD)(rac-1)]OT
f has been determined by NOESY experiments and analysis using the two-dimen
sional conformer population analysis algorithm (2DCPA). The NOESY data reve
al a rapid, pairwise chemical exchange between vinyl protons. The complex [
Rh(NBD)(rac-1)]OTf is a catalyst precursor for hydrogenation reactions. How
ever, we demonstrate that the lability of the aza crown ether may limit the
ability of these catalysts to control selectivity via secondary interactio
ns.