(S,R,Rp)-N,N-Dimethyl-1-{2-[(1-phenylethyl)aminomethyl]ferrocenyl}ethanamine

The title chiral ferrocene compound, [Fe(C5H5)(C18H25N2)], contains one planar and two central chiral centers. It is of interest with respect to asymmetric catalysis. The absolute configuration of the planar chirality is Rp at the ferrocene group and those of the two C chiral centers are R at the CH carbon of the ethanamine unit and S at the CH carbon of the phenylethylamino substituent. In the ferrocenyl unit, the cyclopentadienyl (Cp) rings are planar, with maximum deviations of 0.002 (2) Å for the substituted and 0.008 (3) Å for the unsubstituted Cp ring. The dihedral angle between the ring planes is 2.12 (15)° and the rings are twisted slightly from an eclipsed conformation by 7.06–7.60°.

The title chiral ferrocene compound, [Fe(C 5 H 5 )(C 18 H 25 N 2 )], contains one planar and two central chiral centers. It is of interest with respect to asymmetric catalysis. The absolute configuration of the planar chirality is Rp at the ferrocene group and those of the two C chiral centers are R at the CH carbon of the ethanamine unit and S at the CH carbon of the phenylethylamino substituent. In the ferrocenyl unit, the cyclopentadienyl (Cp) rings are planar, with maximum deviations of 0.002 (2) Å for the substituted and 0.008 (3) Å for the unsubstituted Cp ring. The dihedral angle between the ring planes is 2.12 (15) and the rings are twisted slightly from an eclipsed conformation by 7.06-7.60 .

Experimental
Cg1 is the centroid of the C1-C5 Cp ring and Cg2 is the centroid of the C6-C10 Cp ring.

Comment
Ferrocenes with chirality are increasing their importance as chiral ligands in asymmetric catalysis (Togni, 1996, Nishibayashi et al., 1996. Especially ferrocene-based ligands incorporating both planar and central chirality are very important and some of them have already been applied in hydrogenation, allylic alkylation, and hydroboration (Togni et al., 1994, Dai et al., 2003. We are interested in the synthesis and the fascinating properties of chiral ferrocenes with both central and planar chirality (Liu et al., 2007).
The molecular structure of the title compound is shown in Fig. 1. The absolute configuration of the molecule is Rp at the ferrocene group, R and S at the asymmetric carbon atoms C11 and C16 respectively. Both N atoms have a pyramidal geometry with C-N-C angles between 112.0 (2) and 113.95 (18)°. The N lone-pairs are not involved in short intra-or intermolecular interactions. The two N atoms lie on the same coordination plane and may be available to coordinate to metal ions as bidentate ligands or to act as a ligand for asymmetric catalysis (Nikolaides et al., 2008).
In the molecule, the cyclopentadienyl(Cp) rings are almost parallel with a dihedral angle of 2.12 (15)° between the Cp ring planes. The Cp rings are twisted slightly from the eclipsed conformation. The values of torsion angles of the two Cp rings (C-Cg1-Cg2-C) are in the range 7.06-7.61° (Table 1). The benzene and Cp rings are obviously not parallel. The dihedral angle between the substituted Cp ring and the benzene ring is 53.59 (13)°. The Fe-C bond distances within the ferrocene group are in the range of 2.023 (3)-2.046 (2)Å for the unsubstituted cyclopentadienyl (Cp) ring (C1-C5) and 2.024 (2)-2.052 (2)Å for the substituted Cp ring (C6-C10).

Experimental
(R,Sp)-2-[1-(dimethylamino)ethyl]ferrocenylaldehyde(0.285 g, 1 mmol) was dissolved in anhydrous chloroform (30 ml) and (S)-1-phenylethanamine(0.121 mg, 1 mmol) was added. The red solution was refluxed under a nitrogen atmosphere for 2 h. After removing the solvent, the residue was dissolved in 30 ml dry methanol. 0.160 g NaBH 4 were added in small portions. The mixture was stirred for 30 min, then 20 ml, 1 mol/L aqueous NaOH was added and the mixture was extracted with CHCl 3 (3×30 ml). The combined organic phase was dried with anhydrous NaCO 3 . The solvent was evaporated in vacuo and the residue was purified by column chromatography (silica gel; hexane-ethyl acetate, 6:2) giving the title compound as yellow crystals (0.356 mg, 91.3%). Single crystals were grown from hexane-ethylacetate (2:1) solution at room temperature.

Refinement
All H atoms were placed in geometrically calculated positions and refined using a riding model with C-H = 0.98 Å (for the C 5 H 5 groups), 0.93 Å (for the C 6 H 6 groups) and 0.96 Å (for CH 3 groups), their isotropic displacement parameters were set to 1.2 times (1.5times for CH 3 groups) the equivalent displacement parameters of their parent atoms. The absolute configuration of the structure was determined from the diffraction data using 1859 Friedel pairs with the Flack parameter (Flack, 1983) Fig. 1. The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probabiltiy level and H atoms omitted.