Versatile Behavior of the Schiff Base Ligand 2,5-Me₂C₆H₃C(H)N(2,4,6-Me₃C₆H₂) toward Cyclometalation Reactions: C(sp²,phenyl)−H vs C(sp³,methyl)−H Activation

Treatment of the Schiff base ligand a with palladium(II) acetate in toluene gave 1a, with metalation of an aromatic phenyl carbon atom. Reaction at room temperature gave the trinuclear complex 4a. Treatment of a with palladium(II) acetate in refluxing acetic acid gave 1a′. The reaction of complexes 1a and 1a′ with sodium chloride or lithium bromide gave the halogen-bridged complexes 2a, 3a, 2a′, and 3a′.