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Transition Metal Complexes with Sterically Demanding Ligands. 2. Meisenheimer Complex Formation and Deprotonation Reactions of a Sterically Demanding Aromatic Diimine

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posted on 12.07.2000 by Stefan Nückel, Peter Burger
The synthesis of the novel diimine 1 is described, and its low/absent propensity for the complexation of group 9 transition metals (Co, Rh, 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 1 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 1 and 35 were unambiguously confirmed by X-ray crystal structure analyses.