A General and Facile One‐Step Synthesis of Imido–Titanium(IV) Complexes: Application to the Synthesis of Compounds Containing Functionalized or Chiral Imido Ligands and Bimetallic Diimido Architectures

Abstract

One‐pot reactions of Ti(NMe2)4 with a wide range of primary alkyl, aryl, and silylamines RNH2 in the presence of excess chlorotrimethylsilane produced the corresponding imido–titanium(IV) complexes [Ti(=NR)Cl2(NHMe2)2] (1a–j), in which R = tBu, 1‐adamantane, Ph3C, Ph3Si, Ph, 2,6‐iPr2–C6H3, 2,6‐Cl2–C6H3, 2,6‐Br2–4‐Me–C6H2, C6F5, and 3,5‐(F3C)2–C6H3. This general synthesis, which starts from commercially available reagents, represents a simple and direct route to imido complexes. Reaction of complexes 1 with pyridine afforded the six‐coordinate tris‐pyridine adducts [Ti(=NR)Cl2(Py)3] (2). Another advantage of this method is its tolerance to other functional groups; complexes that contain halides, ether, dialkylamino, cyano, ethynyl, olefin, and nitro substituents on the imido moiety have been prepared. The use of enantiomerically pure primary amines affords the first group of titanium complexes that contain chiral imido groups, and the use of diamines produces diimido complexes. Alternatively, CH3I has been used as an alkylating agent to generate titanium–imido complexes of the type [Ti(NR)I2(THF)2]2. All compounds were fully characterized by spectroscopic methods (IR, 1H NMR, 13C NMR) and elemental analysis. Some of the compounds were also analyzed by single‐crystal X‐ray diffraction studies. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

Arylimido‐Bridged Dinuclear Ti(μ‐NAr)2Ti Scaffold for Alkyne Insertion into the ortho‐C−H Bond of Arylimido Ligands

“…The bond length (2.140(3) Å) of Ti−C12 is typical of a single bond. Notably, the structural features around each titanium atom of 2 a – c were essentially the same as 1 a – c along with some reported imido‐bridged dinuclear titanium complexes…”

“…The planarity of the nitrogen atom of 3 a is deformed, as evidenced by the sum (354.4°) of the bond angles around the nitrogen atom. The dihedral angle between the plane of C14−Ti−N and the plane of the aromatic ring attached on the μ‐imido ligand is 60.5°, and the dihedral angle between the plane of {Ti 2 N 2 } and the plane of the aromatic ring is 58.0°, which is larger than that of 1 a (42.8°) and narrower than that of 2 a (81.5°).…”

“…Herein, we report the synthesis and alkyne‐insertion reaction of a series of dialkyl complexes bearing the bis‐μ‐( N ‐arylimido)dititanium core [{CpTi(CH 2 SiMe 3 )(μ‐NAr)} 2 ] ( 2 a : Ar=Ph; 2 b : Ar=3,5‐Me 2 C 6 H 3 ; 2 c : Ar=3,5‐(CF 3 ) 2 C 6 H 3 ; Cp=cyclopentadienyl), which were prepared by treating μ‐( N ‐arylimido)titanium dinuclear Ti IV –dichloro complexes [{CpTiCl(μ‐NAr)} 2 ] ( 1 a : Ar=Ph; 1 b : Ar=3,5‐Me 2 C 6 H 3 ; 1 c : Ar=3,5‐(CF 3 ) 2 C 6 H 3 ) with LiCH 2 SiMe 3 . We found that, while maintaining the imido‐bridged dinuclear core, complexes 2 a – c treated with 1‐(trimethylsilyl)propyne formed a six‐membered metallacycle through ortho ‐C−H bond activation of the μ‐( N ‐arylimido) ligands (Scheme b).…”

Synthesis, Structures and DFT Studies of Imido‐bridged and (Bis)ligand‐coordinated Titanium Complexes

“…Titanium imido complexes could be approached by several accesses including: (i) reaction of TiCl 4 with pyridine and t BuNH 2 ;12b (ii) treatment of Ti(NMe 2 ) 4 with RNH 2 /Me 3 SiCl/py;14 (iii) transamination of Ti(NMe 2 ) 4 with an ancillary ligand to produce a titanium amido complex, which further reacts with RNH 2 to afford an imido complex 15…”

“…Complexes 3–6 are members of families of titanium complexes with aryl amido bridges,14,26–39 but those complexes with asymmetric Ti2N2 bridges are not common 15b,38,39…”