Generating a New Chiral Ligand System for High-Valent Early Transition Metals — Synthesis and Structural Characterization ofC3-Symmetrical Tripodal Alkyl/Silyl Amido Complexes

The novel C3-chiral tripodal amine HC{SiMe2NH[(S)-3,3-dimethyl-2-butyl]}3 (1) and its trilithium triamido derivative [HC{SiMe2N(Li)[(S)-3,3-dimethyl-2-butyl]}3] (2) have been synthesized and characterized by X-ray diffraction. The lithium reagent was used for the synthesis of a C3-chiral amidozirconium complex [HC{SiMe2N[(S)-3,3-dimethyl-2-butyl]}3ZrCl] (3); the preparation of the analogous titanium compound was precluded by the redox activity of the metal. Instead, the lithium amide-lithium chloride adduct [HC{SiMe2N(Li)[(S)-3,3-dimethyl-2-butyl]}3LiCl(Et2O)3] (4) was isolated from these reactions and structurally characterized by X-ray structure analysis. In this cage compound the chloride ion bridges the three amido lithium atoms and is itself coordinated to an {(Et2O)3Li}+ fragment. Its isolation sheds new light upon the complex reaction sequences leading to halide substitution by a polydentate amido ligand.