4-Fluoro-2-({[(2R)-1-hydroxy-1,1,3-triphenylpropan-2-yl]imino}methyl)phenol

In the title compound, the salicylaldehyde alcohol group is engaged in an intramolecular O—H⋯N hydrogen bond with the imine nitrogen atom, while the tertiary alcohol is engaged in a weak intermolecular O—H⋯F hydrogen bond with an adjacent molecule.


Structure description
We have synthesized a number of chiral imine diols by Schiff-base condensation of the corresponding salicylaldehydes with (S)-or (R)-2-amino-1,1,3-triphenylpropanol Liu et al. 2004). These compounds serve as ligands for titanium for the asymmetric intramolecular hydroamination of aminoallenes (Sha et al., 2019). We routinely prepare both enantiomers of the ligands, and a number of them were examined by single-crystal X-ray diffraction, including the l-enantiomer of the title compound, in order to compare the structures of the free and bound ligand.
2-Hydroxy-5-fluoro-benzaldehyde 2S-(1,1,3-triphenylpropanol) imine, C 28 H 24 FNO 2 , crystallizes in the orthorhombic space group P2 1 2 1 2 1 as shown in Fig. 1. The major structural features of the two enantiomers are similar, as expected. The l-enantiomer structure was collected at 100 K while the d-enantiomer was collected at 293 K. The unitcell parameters in the current room-temperature structure are slightly larger (average 1.3%), presumably due to the higher temperature of the data collection. The absolute structure parameter of À0.1 (3) has a large uncertainty but the absolute configuration was verified by synthesis and polarimetry.

data reports
This deviation is 0.166 Å larger than that for the enantiomer at 100 K, although the torsion angle is almost identical.
There is an intramolecular O2-H2Á Á ÁN1 hydrogen bond (Table 1) between the salicylaldehyde alcohol group and the imine nitrogen atom, which closes an S(6) ring and a longrange intermolecular hydrogen bond between the tertiary alcohol O1-H1 and the F1 atom of an adjacent molecule as shown in Fig. 2: the HÁ Á ÁF and OÁ Á ÁF distances are 2.94 and 3.720 (3) Å , respectively. Weak intermolecular C-HÁ Á ÁF and C-HÁ Á ÁO contacts are also observed.

Synthesis and crystallization
Preparative details of the material have been reported previously (Sha et al., 2019). Crystals in the form of lightyellow blocks were obtained by slow evaporation from the mixed solvents of hexane/ethyl acetate.

Figure 2
A view of the inter-and intramolecular hydrogen-bonding network along the b axis.

Figure 1
The asymmetric unit of the title compound with displacement ellipsoids shown at the 50% probability level. Hydrogen atoms besides H1, H2 and H2A have been omitted for clarity.

Funding information
Funding for this research was provided by: Harvey Mudd College.

data-1
IUCrData ( Special details Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.