Synthesis of Chloro-Substituted β-Ketiminate Palladium Complexes, Spectral and Thermal Investigation of their Structures

The synthesis and characterization of nine palladium(II) complexes featuring β-ketoiminato ligands of type [Pd(ArNacac)₂] (4) with Ar=2-chlorolphenyl (a); 3-chlorophenyl (b); 4-chlorophenyl (c); 2,3-dichlorophenyl (d); 2,4-dichlorophenyl (e); 2,6-dichlorophenyl (f); 3,5-dichlorophenyl (g); 2,4,5-trichlorophenyl (h); 2,4,6-trichlorophenyl (i) is reported. The molecular structure of 4 a–f, 4 h and 4 i in the solid state was confirmed by single-crystal X-ray diffraction studies. All eight crystal structures are centrosymmetric, with the metal positioned in a slightly distorted square plane. Intermolecular non-covalent interactions such as C−H⋅⋅⋅Pd, Cl⋅⋅⋅Cl, Cl⋅⋅ π, C−H⋅⋅⋅Cl, Cl⋅⋅⋅O, C−H⋅⋅ π, and π⋅⋅⋅π play crucial roles in the formation of the supramolecular structures. The crystal structures of 4 b, 4 c, and 4 e revealed unique intermolecular C−H⋅⋅⋅Pd anagostic interactions between the hydrogen atom on the substituted ligand and the palladium centers, which enable the formation of 1-D polymeric chains. The intermolecular non-covalent interactions were analyzed using Hirshfeld surface. The proportional contributions of each individual atom to the formation of these non-covalent interactions are shown in the 2D fingerprint plots. Furthermore, density functional theory (DFT) has been used to compute the energetic estimation of non-covalent interactions in 4 b, 4 c and 4 e. Furthermore, computational methods such the non-covalent interaction (NCI) plot index and quantum theory of atoms in molecules (QTAIM) analysis have been used to study the non-covalent interactions in 4 b, 4 c, and 4 e.