Preliminary catalytic evaluation of zinc(II) and palladium(II) complexes obtained from fluorinated derivatives of 4-(1-benzyl-1H-benzo[d]imidazol-2-yl)thiazole

Carbon‑carbon bond-forming reactions are very important in contemporary organic chemistry, and two of the most widely used protocols are the Knoevenagel–Michael and Suzuki–Miyaura protocols. Therefore, this work explores the catalytic activity of zinc(II) and palladium(II) complexes used in these reactions. To this end, the influence of fluorinated derivatives of 4-(1-benzyl-1 H -benzo[ d ]imidazol-2-yl)thiazole is also analyzed. The fragments analyzed were 1-benzyl for L1 , 1-(3-fluorobenzyl) for L2 , 1-(2,3,6-trifluorobenzyl) for L3 , 1-((perfluorophenyl)methyl) for L4 , and 1-(4-(trifluoromethyl)benzyl) for L5 . The ZnL1 - ZnL5 and PdL1 - PdL5 complexes were obtained from the metalation reactions of L1 - L5 with zinc(II) chloride and bis(acetonitrile)dichloropalladium(II), respectively. All compounds were characterized using various spectroscopic and analytical techniques, and their catalytic activity in the production of 1,8-xanthenedione and 1,1′-biphenyl was tested. In addition, all zinc(II) complexes exhibit catalytic activity in the Knoevenagel–Michael condensation reaction, with ZnL1 exhibiting the highest conversion rate in the synthesis of 1,8-xanthenedione (TON = 75 and TOF = 450 h −1 ). All palladium complexes also exhibit catalytic activity in the Suzuki–Miyaura cross-coupling reaction, with PdL3 exhibiting the highest conversion rate in the synthesis of 1,1′-biphenyl (TON = 42 and TOF = 252 h −1 ). These results show weak catalytic activity in both reactions. • Ten new Zn(II) and Pd(II) complexes were unequivocally characterized. • The amount of fluorine in the ligand does not influence the catalytic activity. • PdL3 showed efficient catalytic activity in Suzuki-Miyaura reactions. • ZnL1 showed efficient catalytic activity in Knoevenagel–Michael reactions • 19 F NMR was an excellent tool in characterising all the complexes.