Transition metal complexes with sterically demanding ligands.: 2.: Meisenheimer complex formation and deprotonation reactions of a sterically demanding aromatic diimine

The synthesis of the novel diimine 1 is described, and its low/absent propensity for the complexation of group 9 transition metals (Co, Ph, Ir) is rationalized by a potentially difficult C-H activation step required for terdentate coordination. To overcome this problem, deprotonation of this unique C-H bond in I with a variety of bases was attempted. The unexpected outcome of these reactions, including the formation of the Meisenheimer complex 3 by addition of butyllithium, is reported. In addition, the formation of the double-addition product 4 through reaction with t-BuLi is described. Deprotonation at the diimine methyl group with the hard base lithium dimethylamide gives the corresponding diketiminate 5. The structures of the novel compounds I-and 3-5 were unambiguously confirmed by X-ray crystal structure analyses.