Nickel(II) complexes containing ONS donor ligands: Synthesis, characterization, crystal structure and catalytic application towards C-C cross-coupling reactions

Nickel(II) complexes containing thiosemicarbazone ligands [Ni(L) 2 ] ( 1 - 3 ) (L = 9,10-phenanthrenequinonethiosemicarbazone (HL 1 ), 9,10-phenanthrenequinone-N-methylthio semicarbazone (HL 2 ) and 9, 10-phenanthrenequinone-N-phenylthiosemicarbazone (HL 3 )) have been synthesized and characterized by elemental analysis and spectroscopic (IR, UV-Vis, 1 H, 13 C-NMR and ESI mass) methods. The molecular structures of complexes 1 and 2 were identified by means of single-crystal X-ray diffraction analysis. The analysis revealed that the complexes possess a distorted octahedral geometry with the ligand coordinating in a uni-negative tridentate ONS fashion. The catalytic activity of complexes towards some C–C coupling reactions (viz., Kumada-Corriu, Suzuki-Miyaura and Sonogashira) has been examined. The complexes behave as efficient catalysts in the Kumada-Corriu and Sonogashira coupling reactions rather than Suzuki-Miyaura coupling. Graphical Abstract Nickel(II) complexes bearing 9,10-phenanthrenequinone N-substituted thiosemicarbazone ligands were synthesized and characterized. The X-ray crystal structure of the complexes revealed a distorted octahedral geometry around the metal centre. These nickel complexes exhibited better catalytic activity in Kumada-Corriu and Sonogashira cross-coupling reactions than in Suzuki-Miyaura reaction.