Bis{(S)-(−)-N-[(2-biphenyl)methylidene]-1-(4-methoxyphenyl)ethylamine-κN}dichloridopalladium(II)

The Pd atom is coordinated by two nitrogen atoms from two trans-aligned imine ligands and two chlorine atoms in an essentially square-planar environment.


Structure description
Schiff bases, derived from the condensation of primary amines and aldehydes, are well established and versatile ligands in coordination chemistry.Their flexibility has led to a diverse range of coordination complexes (Boulechfar et al., 2023).Metal complexes with Schiff base ligands play crucial roles in enhancing catalytic efficiency in various chemical reactions, including oxidation, hydroxylation, aldol condensation, and epoxidation (Gupta & Sutar, 2008;Brayton et al., 2009;Bowes et al., 2011).In addition to their catalytic capabilities, palladium(II) imine complexes exhibit significant biological potential.Their reactivity, influenced by electronic and steric factors, is highly tunable through substituent modifications, particularly with the introduction of chirality.Herein, we report the crystal structure of a novel palladium(II) complex [PdCl 2 (C 22 H 21 NO) 2 ].
The title Pd II complex crystallizes in the monoclinic system with the P2 1 space group.The structure of the trans complex, which contains a single molecule in the asymmetric unit, is shown in Fig. 1.Inspection of the molecular structure confirms the expected square-planar coordination environment around the central palladium(II) atom.The two imine ligands coordinated to the Pd II atom through their nitrogen atoms in a trans configuration, with Pd1-N1 and Pd1-N2 bond lengths of 2.015 (6) and 2.022 (6) A ˚, respectively.The Pd-Cl bond lengths [Pd1-Cl1 = 2.310 (2) A ˚and Pd1-Cl2 = 2.315 (2) A ˚] fall within the expected ranges for this type of complex, which confirms the nature of the bonds.There is a slight distortion from the ideal square-planar geometry, as revealed by a deviation of 0.054 A ˚of the Pd II atom from the plane defined by atoms Cl2-N2-Cl1-N1.The steric effects in the Pd II complex are evident in the torsion angles C26-C23-N2-C24 [À 175.5 ( 7 The closest intermolecular �-� stacking contact between the arene rings is 4.494 A ˚, which is above the typical range of 3.3-3.8A ˚for favorable �-� interactions.Therefore, this interaction does not significantly contribute to the cohesion of the crystal structure.The imine mean planes (C24-N2-C23 and C2-N1-C1) are twisted by 86 (2) and 85 (2) � , respectively, relative to the square-planar coordination mean plane (Cl2/Pd/Cl1).The two attached phenyl rings are not coplanar, as evidenced by the rotation of the mean plane C32-C37 with respect to the mean plane C26-C31 by an angle of 52.8 (4) � .Similarly, the mean plane C10-C15 is rotated with respect to the mean plane C4-C9 by an angle of 43.4 (6) � .
The complex molecules are are stacked parallel to [001].This arrangement is primarily driven by short-range van der Waals interactions and intermolecular hydrogen bonds, particularly C-H� � �Cl interactions (Kinzhalov et al., 2019), detailed in Table 1, which lead to a tri-periodic supramolecular framework (Fig. 2).The square-planar shape of the complex prevents the formation of Pd-Pd or �-� intermolecular interactions, as evidenced by the shortest Pd� � �Pd distance of 10.634A ˚and the shortest �-� distance of 4.494 A ˚, both exceeding van der Waals radii.
While the Pd� � �Pd distances exceed 10 A ˚, indicating minimal direct interaction between palladium atoms, intramolecular Pd� � �H interactions are observed (Fig. 3).These interactions are due to the specific orientations adopted by the phenyl rings (C26-C31 and C4-C9).The distances from the ortho-H atoms in these phenyl rings to the central Pd II atom range from 2.67 A ˚(H27� � �Pd1) to 2.84 A ˚(H5� � �Pd1), suggesting a directional interaction where the ortho-H atoms are oriented towards the Pd II atom.These distances are shorter compared to the Pd� � �H distances involving the CH groups and CH 3 groups within the complex.
A search of the Cambridge Structural Database (CSD, version 5.42, current as of February 2024; Groom et al., 2016) revealed previously reported structures related to the Pd II complex.UQUFIW (Duong et al., 2011)

Figure 2
The crystal packing of the palladium(II) complex ialong [201].The dashed lines indicate intermolecular contacts.All H atoms not involved in these interactions have been omitted for clarity.Displacement ellipsoids are at the 40% probability level.
adopt a trans arrangement due to molecular symmetry, with angles around 90 � .FATQAU and FATPUN (Motswainyana et al., 2012b) crystallize in space group P2 1 /n.The two molecular structures both exhibit a square-planar environment around the palladium atom.In each molecule, the palladium(II) atom is coordinated by two trans-ferrocenylimine molecules via their imine nitrogen atoms, and either two chlorine atoms or a chlorine atom and a methyl group.The structure of LATNAV (Rochon et al., 1993) exhibits hydrogen-bonding interactions between the hydroxyl groups and the chlorido ligands, with the Pd II ion exhibiting a square-planar coordination environment around the central metal atom.YATQAN (Motswainyana et al., 2012a) in P2 1 /n exhibits a square-planar coordination environment around the palladium(II) atom, coordinated by two ferrocenylimine ligands via the imine nitrogen atoms and chlorine atoms.The ferrocenylimine molecules are trans to each other across the center of symmetry.The POCWEN (Anzaldo et al., 2024) complex crystallizes in space group P2 1 , with the central atom tetracoordinated by two nitrogen atoms and two chlorine atoms, resulting in a square-planar configuration.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

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
Experimental details.