Bulky Titanium Amides: C–H Bond Activation under Mild Conditions. Issue 8 (3rd February 2014)

• Record Type: Journal Article
• Authors: Adler, Christian; Bekurdts, Alexander; Haase, Detlev; Saak, Wolfgang; Schmidtmann, Marc; Beckhaus, Rüdiger
• Is Part Of: European journal of inorganic chemistry. Issue 8(2014)
• Page Start: 1289
• Page End: 1302
• Publication Date: 2014-02-03
• Subjects: Titanium -- N ligands -- C–H activation -- Small ring systems -- Structure elucidation; Chemistry, Inorganic -- Periodicals; Organometallic chemistry -- Periodicals; Bioinorganic chemistry -- Periodicals; Solid state chemistry -- Periodicals; 546
• DOI: 10.1002/ejic.201400022
• Languages: English
• ISSNs: 1434-1948

Abstract

Abstract: The bulky titanium monoamido complex Cl3 TiNCy2 (1 ) was synthesized from TiCl4 and dicyclohexylamine (Cy2 NH). The solid‐state structure of1 demonstrates a close intramolecular contact between the metal centre and one ipso carbon atom of the amido ligand. This contact may indicate an agostic interaction analogous to those of transition metal alkyl compounds. The alteration of the coordination sphere of1 with neutral ligands [pyridine (2 ), 2, 2′‐bipyridyl (3 ), N, N, N′, N′ ‐tetramethylethane‐1, 2‐diamine (tmeda, 4 ), and 1, 2‐bis(dimethylphosphanyl)ethane (dmpe, 5 )] results in octahedral compounds with a meridional arrangement of the ligands. The solid‐state structure of5 reveals a significantly closer contact between the titanium atom and one ipso carbon atom of the ligand. The magnesium reduction of1 in the presence of adamantylidenepentafulvene yields the dark green complex (η 5, η 1 ‐adamantylidenepentafulvene)Ti(NCy2 )Cl (8 ). The exchange of the last chlorine atom with other bulky amido ligands [NCy2, N(SiMe3 )2 ] by salt metathesis reactions initiates a spontaneous C–H activation at room temperature. The titanaaziridine (η 5 ‐Cp Ad )(η 2 ‐NCy2 )TiNCy2 (9 ) formed after a β‐C–H activation with LiNCy2 . The use of NaN(SiMe3 )2 results in a γ‐C–H activation and the formation of the azatitanacyclobutane (10 ). The alkylation of ClTi(NCy2 )3 (7 ) with methyllithium produces the reactive complex MeTi(NCy2 )3 (11 ). The spontaneous reaction of11 at room temperature by β‐C–H activation to release methane and cyclohexene yields the dinuclear imido‐bridged complex [(Cy2 N)2 Ti(NCy)]2 (12 ). The formation of12 can also be observed by 1 H NMR spectroscopic measurements. Abstract : The solid‐state structures of tetrahedral and octahedral titanium amide complexes with bulky dicyclohexylamido ligands reveal a characteristic close contact between the titanium atom and a carbon atom in the β‐position. The exchange of a chlorine atom by a bulky pentafulvene ligand increases this effect. The introduction of other sterically demanding amines to complexes initiates a spontaneous C–H activation.