(Alkyl)(pentamethylcyclopentadienyl)tantalum and (alkyl)(alkylidene)(pentamethylcyclopentadienyl)tantalum complexes

• Published in: European journal of inorganic chemistry no. 21; pp. 4242 - 4253
• Main Authors: Galakhov, Mikhail V., Gomez, Manuel, Gomez-Sal, Pilar, Velasco, Patricia
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 06.11.2006
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Physical Sciences; Science & Technology; OLEFIN POLYMERIZATION CATALYSTS; MOLECULAR-STRUCTURE; GROUP-4 METALLOCENE; NEUTRON-DIFFRACTION; alkylidene; AZATANTALACYCLOPROPANE COMPLEXES; RAY CRYSTAL-STRUCTURES; cyclopentadienyl ligands; X-RAY; alkyl; tantalum; ALKYLIDENE-CENTERED REACTIVITY; TANTALUM(V) COMPLEXES; METAL-CARBON BONDS
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.200600173

Alkylation of [TaCp*Cl-4] (Cp* = eta(5)-C5Me5) with 3 equiv. of MgCl(CH2SiMe3) gives the chloridotris(trimethylsilylmethyl) complex [TaCp*Cl(CH2SiMe3)(3)] (1). TaCp*Cl2Me2 reacts with 2 equiv. of LiR (R = CH2Ph, CH2SiMe3) to give the mixed alkyl derivatives [TaCp*Me2R2] (R = CH2Ph, 2; CH2SiMe3, 3). The dimethyldineopentyl complex [TaCp*Me-2(CH2CMe3)(2)] (4) was obtained by reaction of TaCp*Cl-2(CH2CMe3)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*Me-2(CH2CMe2Ph)}(2)(mu-O)] (5), [TaCp*Me-2(CH2CMe2-o-C6H4-kappa C-2,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 degrees 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 SiMe4. However, irradiation of a [D-6] benzene solution of 3 with a sun lamp gave a mixture of 9 and [TaCp*(CH2SiMe3)R(CH2)] (R = Me, 11; CH2SiMe3, 12) in a 2:1:1 (9/11/12) ratio. When a [D-6] benzene solution of 4 was heated at 60 degrees 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*(CH2CMe3)R(CH2)] (R = Me, 15; CH2CMe3, 16) in a 3:1 (15/16) ratio. On the other hand, the alkylation of TaCp*Cl-2(CH2CMe3)(2) with 2 equiv. of LiCH2SiMe3 gave the (alkyl)(alkylidene) complex [TaCp*(CH2CMe3)(CH2SiMe3)(CHCMe3)] (17) with the elimination of SiMe4, whereas the treatment of TaCp*Cl-2(CH2SiMe3)(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. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).