Vinyltitanium Complexes containing the [2-(N,N-Dimethyl-amino)ethyl]tetramethylcyclopentadienyl Ligand Cp*N - Generation and Reactivity of the Vinylidene Intermediate, [(Cp*N)(Cp*)Ti=C=CH2] (Cp*N = h5-C5Me4(CH2)2NMe2, Cp* = h5-C5Me5)
R. Beckhaus , J. Oster, B. Ganter, U. Englert
Organometallics 1997, 16, 3902 - 3909
The reaction of [CpTiCl2]n and Cp*TiCl2(thf) with Cp*NLi (Cp*N: C5Me4CH2CH2NMe2; Cp*: C5Me5) leads to Cp*NCpTiCl (7) and Cp*NCp*TiCl (8), respectively. The monochlorides are oxidized by PbCl2 to give Cp*NCpTiCl2 (9) and Cp*NCp*TiCl2 (10). The molecular structures of 7 and 10 have been determined by X-ray diffraction analysis, which reveal a chelating bonding mode of the Cp*N-ligand in 7 (Ti-N: 2.437(3) Å) and noncoordination of the NMe2-group in 10. The fulvene complex Cp*N(C5Me4CH2)TiCH=CH2 (18) and the titanacyclobutane Cp*NCp*TiCH2CH2C=CH2 (14), respectively, are formed under mild conditions via the titanocenevinylidene intermediate [Cp*NCp*Ti=C=CH2] (17), generated by a-H-transformation from the vinylcomplexes Cp*NCp*Ti(CH=CH2)(CH3) (15) and Cp*NCp*Ti(CH=CH2)2 (12). The formation of 14 is discussed to be influenced by the nitrogen containing side chain in the Cp*N-ligand. A stabilization of 17 by intramolecular Ti-N coordination is not observed under the reaction conditions. Intermolecular trapping of 17 with transition metal carbonyls M(CO)6 leads to the heterobinuclear titanaoxetanes Cp*NCp*TiOC(=M(CO)5)C=CH2 (21, M = Cr (a), W (b)).