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

Abstract

Low-coordinate titanium(III) amido complexes were readily prepared via treatment of β-TiCl 3 with 1 or 2 equiv of Li[N(Si i Pr 3 )DIPP] (DIPP = 2,6-di-iso-propylphenyl) to form dinuclear [{Ti(N(Si i Pr 3 )DIPP)Cl(μ-Cl)} 2 ] (1) or mononuclear Ti[N(Si i Pr 3 )DIPP] 2 Cl (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 LiCH 2 SiMe 3 to form mono-or dialkyl products, respectively. In contrast, treatment of complex 1 in the absence of DMAP with 2 equiv of LiCH 2 SiMe 3 results in the ultimate formation of a dinuclear cyclometalated complex 9 bearing a [Ti 2 (μ-Cl) 2 (μ:η 1 -CH 2 SiMe 2 CH 2 -)] 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.

A Mixed-Valence Ti(II)/Ti(III) Inverted Sandwich Compound as a Regioselective Catalyst for the Uncommon 1,3,5-Alkyne Cyclotrimerization

“…The less acidic Ti(III) metal center results in elongated Ti–N bonds [average = 2.01(1) Å] than those registered for 2 (1.970(5) Å). Compared to structurally characterized aryl-amide Ti(III) species, 33 these bond lengths are also lengthened by ca. 0.1 Å; however, they are similar to the Ti(III) amide compounds reported by our group [Li(thf) 4 ][Ti( Ar PDA) 2 ] 27 (Ar = 2,4,6-trimethylphenyl and 2,6-diisopropylphenyl) and for the nitrile- and isocyanide-solvated titanium amido compounds [Ti(N(SiMe 3 ) 2 ) 3 L 2 ].…”

Putting on the Crown: Synthesis and Reactivity of Trimethyltitanium

“…The Ti–C distances of 2.180(4) and 2.189(4) Å are significantly shorter than those in complex 1 , while the Ti–Cl distance of 2.4122(14) Å is longer than that in the trichlorido precursor (2.345(1)–2.356(1) Å) . For further comparison, a four-coordinate trivalent complex [(C 6 H 3 i Pr 2 -2,6)( i Pr 3 Si)N]TiCl(CH 2 SiMe 3 )(DMAP) shows Ti–Cl and Ti–C distances of 2.3303(7)/2.3474(9) and 2.126(3)/2.131(2) Å, respectively …”

“…11 For further comparison, a fourcoordinate trivalent complex [(C 6 H 3 iPr 2 -2,6)(iPr 3 Si)N]TiCl-(CH 2 SiMe 3 )(DMAP) shows Ti−Cl and Ti−C distances of 2.3303(7)/2.3474(9) and 2.126(3)/2.131(2) Å, respectively. 15 Derivatization of (Me 3 TACN)TiMe 3 (1). Initial methyl group displacement was probed with the trimethylsilane (TMS) derivatives ClSiMe 3 and TfOSiMe 3 (OTf = CF 3 SO 3 − , triflato).…”