(S)-(+)-1-(4-Bromophenyl)-N-[(4-methoxyphenyl)methylidene]ethylamine and bis{(S)-(+)-1-(4-bromophenyl)-N-[(4-methoxyphenyl)methylidene]ethylamine-κN}dichloridopalladium(II)

The synthesis, crystal structure and analysis of a chiral Schiff base (S)-(+)-1-(4-bromophenyl)-N-[(4-methoxyphenyl)methylidene]ethylamine ligand along with its corresponding palladium(II) complex are detailed. The crystal structures exhibit monoclinic P21 and orthorhombic P212121 symmetries, respectively. The structure of the palladium(II) complex reveals C—H⋯O and C—H⋯Br hydrogen-bonding interactions involving two distinct molecules within the asymmetric unit.


Chemical context
Schiff base ligands commonly result from the condensation of primary amines and aldehydes.The ease of their synthesis and the flexibility of their chemical structures make Schiff bases widely used in coordination chemistry, with a wide range of coordination complexes (Boulechfar et al., 2023).The catalytic prowess of Schiff base complexes with metal centres is well documented and shows enhanced activity in various chemical reactions (Gupta & Sutar, 2008).Their catalytic potential extends to processes such as oxidation, hydroxylation, aldol condensation and epoxidation (Brayton et al., 2009;Hu et al., 2016;Bowes et al., 2011).Changes in the substituents of the imine compounds affect their reactivity, influenced by electronic and steric factors that affect their structure.In particular, some imine compounds present conjugated electron systems and have attracted attention for their optical and materials properties (Kalita et al., 2014;Anzaldo et al., 2019;Cı ˆrcu et al., 2006).The presence of chirality in the structures enhances a valuable dimension for catalyst design, allowing for fine-tuning and selectivity in a variety of chemical reactions.Here we report the crystal and molecular structure of the chiral Schiff base (S)-(+)-1-(4-bromophenyl)-N-[(4methoxyphenyl)methylidene]ethylamine, (I), and its palladium(II) complex, bis{(S)-(+)-1-(4-bromophenyl)-N-[(4methoxyphenyl)methylidene]ethylamine-�N}dichloridopalladium(II), (II), which has not been reported previously.

Structural commentary
The ligand crystallizes in the orthorhombic system with the space group P2 1 2 1 2 1 .Within the asymmetric unit, there is a single molecule, as depicted in Fig. 1.The length of the C9 N1 double bond is 1.265 (7) A ˚.The imine group exhibits a C1-N1-C9 angle of 118.1 (6) � .The bond lengths and angles confirm the sp 2 hybridization for the C and N atoms.
The palladium(II) complex crystallizes within the monoclinic system, space group P2 1 .The structure contains two independent molecules (labelled as A and B) within the asymmetric unit, as illustrated in Fig. 2. The length of the C N bond is comparable to that observed in the ligand.

Figure 2
The molecular structure of the two molecules units in the asymmetric unit of the title palladium(II) complex, (II).Displacement ellipsoids are drawn at the 50% probability level.
1.285 A ˚.These bond lengths and angles provide confirmation of the sp 2 hybridization of the C and N atoms.The crystal structure of the Pd II complex shows disorder in the two Br atoms in molecule B of the asymmetric unit.

Supramolecular features
The arrangement of the ligand molecule arises from short contacts corresponding to van der Waals interactions.Intermolecular distances are calculated from atomic coordinate translations along the a axis, revealing short C-H� � �C contacts (Nishio 2004;Enamullah et al., 2007;Brandl et al., 2001).Specific interactions include H11� � �C13 at 2.855 A ˚and H8� � �C16 at 2.836 A ˚, as shown in Fig. 3.The self-assembly of the palladium(II) complex forms a three-dimensional structure through intermolecular hydrogen bonds involving C-H� � �O, C-H� � �Cl, C-H� � �Br and C-H� � �C interactions (Desiraju, 1996;Steiner, 1997;Kinzhalov et al., 2019).As a result, a packing arrangement of supramolecular layers is produced, as depicted in Fig. 4. The molecular array is influenced by all the contacts, as detailed in Table 1.
In the case of the complex of Pd II , some previously reported structures include LATNAV (Rochon et al., 1993), in which the structure is stabilized through hydrogen-bonding interactions between the hydroxy groups and the chloride ligands, with the Pd II ion exhibiting square-planar coordination Growth in the projection on the bc plane (displacement ellipsoids are presented with 50% probability), with dashed lines indicating intermolecular contacts.All H atoms not involved in these interactions have been omitted for clarity.

Figure 4
The crystal packing diagram of palladium(II) complex (II).The dashed lines indicate intermolecular hydrogen bonds (displacement ellipsoids are presented with 50% probability).All H atoms not involved in these interactions have been omitted for clarity.
geometry around the metal centre in the space group P2 1 /c.FATQAU and FATPUN (Motswainyana et al., 2012b) crystallizes in the space group P2 1 /n.The two molecular structures exhibit square-planar geometry around the Pd atom.In each molecule, the Pd atom is coordinated to two transferrocenylimine molecules via their imine N atoms, and either two chlorides or a chloride and a methyl.UQUFIW (Duong et al., 2011) crystallizes in the space group P1.The chloride and (pyridin-4-yl)boronic acid ligands adopt a trans arrangement due to molecular symmetry, and angles are about 90 � .YATQAN (Motswainyana et al., 2012a) crystallizes in the space group P2 1 /n.The Pd II ion has square-planar coordination geometry around the metal centre, coordinated to two ferrocenylimine ligands via the imine N atoms and the chloride ions.The ferrocenylimine molecules are trans with respect to each other across the centre of symmetry.

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.Refinement.X-ray diffraction was recorded by Rigaku Oxford diffractometer with graphite-monochromated Mo Kα radiation (0.71073 Å).CrysAlis PRO software (Agilent, 2014) was employed for data reduction.The structures were solved through intrinsic phasing and direct methods, employing SHELXS (Sheldrick, 2008) and SHELXT (Sheldrick, 2015a).Non-H atoms were refined anisotropically, while H atoms were geometrically placed and refined with isotropic displacement parameters using the riding model in the SHELXL2019 program (Sheldrick, 2015b).Molecular graphics: OLEX2 (Dolomanov et al., 2009)

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.

Table 2
Rigaku OD, 2015)ails.For all structures: Z = 4. Experiments were carried out at 293 K with Mo K� radiation using a Rigaku Xcalibur Atlas Gemini diffractometer.The absorption correction was analytical (CrysAlis PRO;Rigaku OD, 2015).H-atom parameters were constrained.