935863-69-7Relevant academic research and scientific papers
(Alkyl)- and (alkyl)(alkylidene)(pentamethylcyclopentadienyl)tantalum complexes
Galakhov, Mikhail V.,Gomez, Manuel,Gomez-Sal, Pilar,Velasco, Patricia
, p. 4242 - 4253 (2006)
Alkylation of [TaCp*Cl4] (Cp* = η5- C5Me5) with 3 equiv. of MgCl(CH2SiMe 3) gives the chloridotris(trimethylsilylmethyl) complex [TaCp*Cl(CH2SiMe3)3] (1). TaCp*Cl2Me2 reacts with 2 equiv. of LiR (R = CH 2Ph, CH2SiMe3) to give the mixed alkyl derivatives [TaCp*Me2R2] (R = CH2Ph, 2, CH2SiMe3, 3). The dimethyldineopentyl complex [TaCp*Me2(CH2-CMe3)2] (4) was obtained by reaction of TaCp*Cl2-(CH2CMe 3)2 with 2 equiv. of LiMe. The treatment of a toluene solution of TaCp*Cl2Me2 with 2 equiv. of neophyllithium in a standard vacuum line gave a mixture of three compounds, [{TaCp*Me2(CH2CMe2Ph)} 2(μ-O)] (5), [TaCp*Me2(CH2CMe 2-o-C6H4-κ2C,C)] (6) and [TaCp*Me(CH2CMe2Ph)-(CH2)] (7), which were identified by NMR spectroscopy. However, when the reaction was carried out under rigorously anhydrous conditions, only complexes 6 and 7 were isolated. A chlorido(trimethylsilylmethyl)(trimethylsilylmethylidene) complex [TaCp*Cl(CH2SiMe3)(CHSiMe3)] (8) was prepared by heating 1 at 60°C, or by leaving it at room temperature for a long time. A 3:2 (9/10) mixture of [TaCp*MeR-(CHSiMe3)] (R = CH2SiMe3, 9; Me, 10) was obtained by thermal treatment of 3, which was accompanied by the evolution of CH4 and SiMe 4. However, irradiation of a [D6]benzene solution of 3 with a sun lamp gave a mixture of 9 and [TaCp*(CH2SiMe 3)R(CH2)] (R = Me, 11; CH2SiMe3, 12) in a 2:1:1 (9/11/12) ratio. When a [D6]benzene solution of 4 was heated at 60°C, a mixture of the (alkyl)(neopentylidene) derivatives [TaCp*MeR(CHCMe3)] (R = Me, 13; CH2CMe3, 14) in a 4:1 (13/14) ratio was detected by NMR spectroscopy, while irradiation with a sun lamp produced a mixture of alkylidene complexes [TaCp*(CH 2CMe3)R(CH2)] (R = Me, 15; CH 2CMe3, 16) in a 3:1 (15/16) ratio. On the other hand, the alkylation of TaCp*Cl2(CH2CMe3) 2 with 2 equiv. of LiCH2SiMe3 gave the (alkyl)(alkylidene) complex [TaCp*(CH2CMe3)(CH 2SiMe3)(CHCMe3)] (17) with the elimination of SiMe4, whereas the treatment of TaCp*Cl2-(CH 2SiMe3)2 with the appropriate reagent gave [TaCp*(CH2R)(CH2SiMe3)(CHR′)] (R = R′ = Ph, 18; R = CMe2Ph, R′ = SiMe3, 19) with the elimination of SiMe4 and CMe3Ph, respectively. All compounds were studied by IR and NMR spectroscopy, and the molecular structures of complexes 1, 4 and 5 were determined by X-ray diffraction methods. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
