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(Si^<i>i</i>Pr₃)­DIPP] (DIPP = 2,6-di-<i>iso</i>-propylphenyl) to form dinuclear [{Ti­(N­(Si^<i>i</i>Pr₃)­DIPP)­Cl­(μ-Cl)}₂] (<b>1</b>) or mononuclear Ti­[N­(Si^<i>i</i>Pr₃)­DIPP]₂Cl (<b>2</b>), 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 <b>1</b> was shown to be a versatile precursor for salt metathesis reactions to form heteroleptic complexes bearing alkoxide or silyl ligands. Alternatively, <b>1</b> formed adducts with Lewis bases such as 4-dimethylaminopyridine (DMAP) that are paramagnetic, mononuclear species. The base-stabilized complex <b>5</b> was alkylated with 1 or 2 equiv of LiCH₂SiMe₃ to form mono- or dialkyl products, respectively. In contrast, treatment of complex <b>1</b> in the absence of DMAP with 2 equiv of LiCH₂SiMe₃ results in the ultimate formation of a dinuclear cyclometalated complex <b>9</b> 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.