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Bulky Titanium Amides: C–H Bond Activation under Mild Conditions
Author(s) -
Adler Christian,
Bekurdts Alexander,
Haase Detlev,
Saak Wolfgang,
Schmidtmann Marc,
Beckhaus Rüdiger
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201400022
Subject(s) - chemistry , agostic interaction , ligand (biochemistry) , medicinal chemistry , coordination sphere , hexacoordinate , intramolecular force , methyllithium , octahedron , metathesis , pyridine , reductive elimination , metal , stereochemistry , crystallography , crystal structure , organic chemistry , catalysis , polymerization , biochemistry , receptor , silicon , polymer
The bulky titanium monoamido complex Cl 3 TiNCy 2 ( 1 ) was synthesized from TiCl 4 and dicyclohexylamine (Cy 2 NH). The solid‐state structure of 1 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 of 1 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 of 5 reveals a significantly closer contact between the titanium atom and one ipso carbon atom of the ligand. The magnesium reduction of 1 in the presence of adamantylidenepentafulvene yields the dark green complex (η 5 ,η 1 ‐adamantylidenepentafulvene)Ti(NCy 2 )Cl ( 8 ). The exchange of the last chlorine atom with other bulky amido ligands [NCy 2 , N(SiMe 3 ) 2 ] by salt metathesis reactions initiates a spontaneous C–H activation at room temperature. The titanaaziridine (η 5 ‐Cp Ad )(η 2 ‐NCy 2 )TiNCy 2 ( 9 ) formed after a β‐C–H activation with LiNCy 2 . The use of NaN(SiMe 3 ) 2 results in a γ‐C–H activation and the formation of the azatitanacyclobutane ( 10 ). The alkylation of ClTi(NCy 2 ) 3 ( 7 ) with methyllithium produces the reactive complex MeTi(NCy 2 ) 3 ( 11 ). The spontaneous reaction of 11 at room temperature by β‐C–H activation to release methane and cyclohexene yields the dinuclear imido‐bridged complex [(Cy 2 N) 2 Ti(NCy)] 2 ( 12 ). The formation of 12 can also be observed by 1 H NMR spectroscopic measurements.