Sonogashira Coupling (Cu/Amine-Free) of ArBr/Cl in Aerobic Condition and N-Benzylation of Aniline with Benzyl Alcohol Catalyzed by Complexes of Pd(II) with Sulfated/Selenated NHCs

The moisture and air insensitive, and thermally stable [Pd(L1/L2-H)Cl][PF₆] (1/2) and [Pd(L3/L4-HI)Cl₂] (3/4) catalyze N-benzylation of aniline (at 100 °C) and Sonogashira coupling of ArBr/Cl (at 80 °C) in the presence of KOH and K₂CO₃ respectively. The optimum catalyst loading (mol %) is 0.02-0.1 for the C−C coupling and 0.5 for N-benzylation. The 1–4 were found reusable. The L1/L2=3-(1-benzyl-1H-1,2,3-triazol-4-yl)methyl)-1-(2-(phenyl thio/seleno)ethyl)-1H-benzo[d]imidazol-3-ium hexafluorophosphate and L3/L4=4-methyl-1-(2-(phenylthio/seleno)ethyl)-1H-1,2,4-triazol-4-ium iodide are precursors of N-heterocyclic carbenes. Copper-catalyzed click reaction gave L1/L2. The treatment of triazole with ClCH₂CH₂Cl, [PhS/Se]⁻Na⁺ and MeI successively afforded L3/L4. The sequence of reactions of L1-L4 with Ag₂O and [Pd(CH₃CN)₂Cl₂] (M : L=1 : 1) gave 1–4. The L1-L4 and 1–4 were characterized by elemental analyses, multi-nuclei NMR, HR-MS and single-crystal structure (3 and 4). The geometry of Pd in 3/4 is nearly square planar. The bond distances (Å) in 3/4 are: Pd−S/Se, 2.3040(7)/2.402(2) and Pd−C, 1.961(3)/1.938(11).