Vinyltitanium Complexes Containing the [2-(N,N-Dimethylamino)ethyl]tetramethylcyclopentadienyl Ligand Cp*^N. Generation and Reactivity of the Vinylidene Intermediate [(Cp*^N)(Cp*)TiCCH₂] (Cp*^N= η⁵-C₅Me₄(CH₂)₂NMe₂, Cp* = η⁵-C₅Me₅)

Abstract

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 reveals 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)TiCHCH2 (18) and the titanacyclobutane respectively, are formed under mild conditions via the titanocenevinylidene intermediate [Cp*NCp*TiCCH2] (17), generated by α-H transformation from the vinyl complexes Cp*NCp*Ti(CHCH2)(CH3) (15) and Cp*NCp*Ti(CHCH2)2 (12). The formation of 14 is suggested 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 (21, M = Cr (a), W (b)).