A new palladium complex series with N-heterocyclic carbene (NHC), pyridine and phosphine ligands, PdCl₂(L)NHC (2a–c)(L = NHC), PdCl₂(L¹)NHC(3a–c)(L¹ = pyridine), PdCl₂(L²)NHC(4a–c)(L² = triphenylphosphine) was synthesised and fully characterized.

A novel series of N-heterocyclic carbene-phosphine palladium(II) complexes has been synthesized and fully characterized by IR, ¹H NMR, ¹³C NMR, and ³¹P NMR spectroscopies, and elemental analysis. The new N-heterocyclic carbene (NHC)-phosphine palladium(II) complexes 3a–h have been easily prepared by the reaction of the corresponding PEPPSI (pyridine-enhanced precatalyst preparation stabilization and initiation) complexes 2a–h and triphenylphosphine in dichloromethane in high yields. These complexes were applied as catalyst precursors which efficiently catalyzed Sonogashira reactions between aryl bromides and phenylacetylene to afford the corresponding products in good yields. The bulky NHC-Pd-PPh₃ complexes 3 were tested against Gram-positive and Gram-negative bacteria to study their biological activity. All the complexes exhibit antibacterial against these organisms. Investigation of the anti-acetylcholinesterase activity of the studied complexes showed that compounds 3a and 3b exhibited moderate activity at 100 μg mL⁻¹ and product 3b is the most active.

A series of ruthenium( ii ) complexes with N-heterocyclic carbene ligands were successfully synthesized by transmetalation reactions between silver( i ) N-heterocyclic carbene complexes and [RuCl ₂ ( p -cymene)] ₂ in dichloromethane under Ar conditions.

New palladium complexes were efficiently synthesized from the reaction of benzimidazolium salts 2a–e, potassium carbonate (K₂CO₃) and palladium chloride (PdCl₂) in pyridine (for 3a–e). The catalytic activity of these complexes in a catalytic system including palladium complexes and K₂CO₃ in DMF-H₂O was evaluated in Suzuki–Miyaura cross-coupling reactions of aryl bromides and chlorides with phenylboronic acid. Our novel complexes show excellent catalytic activities with high turnover numbers (TON) and high turnover frequencies (TOF) (e.g. for the Suzuki–Miyaura reaction: TON up to 370 and TOF up to 123.3 h⁻¹). Both benzimidazolium salts 2a–e and complexes 3 have been characterized using spectroscopic data and elemental analysis. The antimicrobial activity of the N-heterocyclic carbene palladium complexes 3a–e varies with the nature of the ligands. Also, the IC₅₀ values of both, complexes (3a–e) and benzimidazoles 2a–e, have been determined. In addition, the new palladium complexes were screened for their antitumor activity. Complexes 3e and 3d exhibited the highest antitumor effect with IC₅₀ values 6.85 μg/mL against MCF-7 and 10.75 μg/mL against T47D, respectively.