2-((Z)-{3-[(Z)-(2-Hydroxy-5-methylbenzylidene)amino]-2,2-dimethylpropyl}iminomethyl)-4-methylphenol

In the title compound, C21H26N2O2, the dihedral angle between the two benzene rings is 73.47 (16)°. Strong intramolecular O—H⋯N hydrogen bonds generate S(6) ring motifs. The substituted benzene rings are twisted around the central quaternary C atom in opposite directions, making a vault geometry.

In the title compound, C 21 H 26 N 2 O 2 , the dihedral angle between the two benzene rings is 73.47 (16) . Strong intramolecular O-HÁ Á ÁN hydrogen bonds generate S(6) ring motifs. The substituted benzene rings are twisted around the central quaternary C atom in opposite directions, making a vault geometry.

Related literature
For standard bond lengths, see: Allen et al. (1987). For hydrogen-bond motifs, see: Bernstein et al. (1995). For related structures, see: Kargar et al. (2009Kargar et al. ( , 2010 Table 1 Hydrogen-bond geometry (Å , ).  The asymmetric unit of the title compound, Fig. 1, comprises a potentially tetradenate Schiff base ligand. The bond lengths (Allen et al., 1987) and angles are within the normal ranges. The dihedral angle between the two phenyl rings is 73.47 (16)°.
Strong intramolecular O-H···N hydrogen bonds generate S(6) ring motifs (Bernstein et al., 1995). The title compound has a skew geometry. In the absence of sufficient anomalous scattering the absolute structure could not be determined.

Experimental
The title compound was synthesized by adding 5-methyl-salicylaldehyde (4 mmol) to a solution of 2,2'-dimethylpropylenediamine (2 mmol) in ethanol (20 ml). The mixture was refluxed with stirring for half an hour. The resultant yellow solution was filtered. Yellow single crystals of the title compound suitable for X-ray structure determination were recrystallized from ethanol by slow evaporation of the solvents at room temperature over several days.

Refinement
H atoms of the hydroxy groups were located by a rotating O-H group and constraied to refine with the parent atoms with U iso (H) = 1.5 U eq (O), see Table 1. The remaining H atoms were positioned geometrically with C-H = 0.93-0.97 Å and included in a riding model approximation with U iso (H) = 1.2 or 1.5 U eq (C). A rotating group model was used for the methyl groups of the benzene rings. In the absence of sufficient anomalous scattering the absolute structure could not be determined and 1580 Friedel pairs were merged.

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 supplementary materials sup-3 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.
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 > 2sigma(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.