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 G-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-buty1]}(3)] (2) have been synthesized and characterized by X-ray diffraction. The Lithium reagent was used for the synthesis of a C-3-chiral amido-zirconium complex [HC{SiMe2N[(s)-3,3-dimethyl-2-butyl]}(3)ZrCl] (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{siMe(2)N(Li)[(s)-3,3-dimethyl-2-butyl]}(3)LiCl(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)(3)Li}(+) fragment. Its isolation sheds new light upon the complex reaction sequences leading to halide substitution by a polydentate amido ligand.