Synthesis, Characterization, and Reactivity of Low-Coordinate Titanium(III) Amido Complexes

Low-coordinate titanium(III) amido complexes were readily prepared via treatment of β-TiCl3 with 1 or 2 equiv of Li[N(SiiPr3)DIPP] (DIPP = 2,6-di-iso-propylphenyl) to form dinuclear [{Ti(N(SiiPr3)DIPP)Cl(μ-Cl)}2] (1) or mononuclear Ti[N(SiiPr3)DIPP]2Cl (2), respectively. Both complexes were characterized by a variety of methods, including NMR spectroscopy, Evans method magnetic susceptibility, and single-crystal X-ray diffraction studies. Complex 1 was shown to be a versatile precursor for salt metathesis reactions to form heteroleptic complexes bearing alkoxide or silyl ligands. Alternatively, 1 formed adducts with Lewis bases such as 4-dimethylaminopyridine (DMAP) that are paramagnetic, mononuclear species. The base-stabilized complex 5 was alkylated with 1 or 2 equiv of LiCH2SiMe3 to form mono- or dialkyl products, respectively. In contrast, treatment of complex 1 in the absence of DMAP with 2 equiv of LiCH2SiMe3 results in the ultimate formation of a dinuclear cyclometalated complex 9 bearing a [Ti2(μ-Cl)2(μ:η1-CH2SiMe2CH2-)] core. This study demonstrates the convenient synthesis of a family of low-coordinate titanium(III) amido complexes possessing a variety of neutral and monoanionic ligands.