Application of Transition‐Metal Complexes in Cyclohexane Oxidation: Synthesis, Structure, and Properties of Copper and Nickel Complexes with a Pincer N‐Heterocyclic Ligand

Abstract A series of coordination complexes, [CuCl 2 (H 2 L)] ( 1 ), [Ni(HL) 2 ] ⋅ 4 CH 3 CH 2 OH ( 2 ), [Cu(H 2 L)(dipic)] ⋅ 0.5 HOCH 2 CH 2 OH ⋅ 2 H 2 O ( 3 ), and [Ni(H 2 L)(dipic)] ⋅ 0.5 HOCH 2 CH 2 OH ⋅ 2 H 2 O ( 4 ) (H 2 L=2,6‐di(5‐methyl‐1 H ‐pyrazol‐3‐yl)pyridine, H 2 dipic=2,6‐pyridinedicarboxylic acid) are synthesized from bipyrazolyl derivative ligands. All of the complexes have been characterized by elemental analysis, IR and UV/Vis spectroscopy, powder X‐ray diffraction, and single‐crystal X‐ray diffraction. Structural analyses reveal that the H 2 L ligand in complexes 1–4 connects with one metal center in a tridentate manner. In addition, these complexes are potential catalysts in cyclohexane (Cy) oxidation with an acidic mixture of HCl and lactic acid. A putative mechanism for Cy oxidation promoted by complex 2 is also proposed.