The modulation of the structures and electronic properties of transition metal complexes by multi-ligands coordination has been widely exploited to enhance the catalytic?efficiency in organic transformations. Here, we present synthesis, characterization, and catalytic performance of Cu(II), Ni(II) and Pd(II) complexes of multidentate ligands- EDTA, 1,10-phenanthroline and?N-heterocyclic carbenes (NHCs). The Pd-NHC complex displayed the high catalytic activity for hydrogenation as well as?small-molecule activation, up to 450 h?¹ of turnover frequency (TOF) and total conversion of styrene to ethylbenzene at room temperature, and is higher efficient than Cu-EDTA (TOF =120 h?¹), Ni-Phen (TOF= 85 h?¹). The DFT calculation with Pd-NHC system showed that the small HOMO-LUMO gap (3.2 eV) and the short Pd–C bond (1.95 Å) of Pd-NHC,?which could facilitate the transfer of the growth species, contributed to the low energy of activation (28 kJ/mol). Mathematical?model also discussed its high catalytic activity (TOF/Ea = 16.07 h?¹·kJ?¹·mol) due to the strong ?-donor ligands and proper geometry. These findings underscore the influence of ligand architecture to secure transition states and modulate electron density in designing efficient sustainable catalysis that is?industrially relevant.
