( R )-2-Ferrocenyl-4-hydroxymethyl-4,5-dihydro-1,3-oxazole

The title compound, [Fe(C5H5)(C9H10NO2)], was prepared from ferrocenecarboxylic acid and serine. In the crystal structure, mol­ecules are arranged in chains with an inter­molecular hydrogen bond between hydr­oxy groups and N atoms.

The title compound, [Fe(C 5 H 5 )(C 9 H 10 NO 2 )], was prepared from ferrocenecarboxylic acid and serine. In the crystal structure, molecules are arranged in chains with an intermolecular hydrogen bond between hydroxy groups and N atoms.

Comment
A series of serine-derived oxazoles has been shown to be effective in asymmetric alkylation reactions, and hence their crystal structures are of interest (Jones & Richards, 2004). As representatives of the general amino alcohol class of ligands for these reactions, we have an interest in understanding their non-linear catalytic characteristics. A single-crystal X-ray structure has been reported for a related compound, viz. (4S)-4-(1-hydroxy-1-methylethyl)-2-ferrocenyl-4,5-dihydro-1,3oxazole monohydrate (Chesney et al., 1998).
The structure of the title compound, (I) (Fig. 1), reveals that the two cyclopentadienyl rings of ferrocene deviate by only four degrees from a fully eclipsed conformation. The torsion angle C1-C1c-C2c-C11 (where C1c and C2c are the cycopentadiene ring centroids) is À3.5 (6) . The oxazoline ring is almost coplanar with the cyclopentadienyl ring to which it is attached [interplanar angle = 9.2 (5) and C2-C1-C6-O1 = À6.3 (10) ], the O rather than the N atom being slightly closer to iron. The oxazoline hydroxymethyl substituent is oriented away from the iron-cyclopentadienyl group of ferrocene. Significantly, the opposite rotamer, with respect to rotation about the ferrocene-oxazoline C-C -bond, was observed in the structure reported by Chesney et al. (1998). This contains a larger 1-hydroxy-1-methylethyloxazoline substituent, and in both cases the hydroxy group is oriented over the oxazoline ring; in the present structure, N1-C8-C9-O2 = À73.7 (7) .
H atoms were treated as riding atoms [C-H = 0.95 and 0.99 Å ; U iso (H) = 1.2U eq (C)]), except for H20, which was refined freely with an isotropic displacement parameter.

Figure 1
The molecular structure of (I). Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.

Figure 2
The polymeric assembly of (I), involving hydrogen-bonded (dashed lines) oxazole groups. Special details Experimental. Number of psi-scan sets used was 3 Theta correction was applied. Averaged transmission function was used. No Fourier smoothing was applied. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.