Alkyl chloro, dialkyl and mixed alkyl derivatives of imido(pentamethylcyclopentadienyl) tantalum(V).: X-ray crystal structure of [TaCp*Cp′Cl{N(2,6-Me2C6H3)}], (Cp′ = η5-C5H4SiMe3)

[TaCp*Cl-2{N(2,6-Me2C6H3)}] (Cp* = eta(5)-C5Me5) reacts with one equivalent of LiR (R = CH2SiMe3, CH2CMe2Ph, CH2CMe3, 2-(CH2NMe2)C6H4, C5H4SiMe3) or 0.5 equivalents of Mg(CH2C6H5)(2)(THF)(2) to give the alkyl chloro complexes [TaCp*ClR{N(2,6-Me2C6H3)}],(R = CH2SiMe3, 1; CH2CMe2Ph, 2; CH2CMe3, 3; CH2C6H5, 4; 2-(CH2NMe2)C6H4, 5; C5H4SiMe3, 6). When the same reaction was carried out with two equivalents of lithium or one equivalent of magnesium reagent, the corresponding dialkyl derivatives [TaCp*R-2{N(2,6-Me2C6H3)}],(R = CH2SiMe3, 7; CH2CMe2Ph, 8; C6H5, 9; CH2C6H5, 10; CH2CMe3, 11) were obtained. The mixed alkyl derivatives [TaCp*MeR{N(2,6-Me2C6H3)}],(R = CH2SiMe3, 12; CH2CMe2Ph, 13; C6H5, 14; CH2CMe3, 15; 2-(CH2NMe2)C6H4, 16; CH2C6H5, 17; C5H4SiMe3, 18) have been prepared by treatment of solutions containing [TaCp*ClMe{N(2,6-Me2C6H3)}] with one equivalent of lithium or 0.5 equivalents of magnesium reagent. All the new complexes were characterized by the usual IR and NMR spectroscopic methods. The crystal structure of 6 was determined by X-ray diffraction studies. Crystals of 6 are monoclinic, space group P2(1)/c, with Z = 4 in a unit cell of dimensions a = 12.597(3), b = 11.338(2), c = 18.297(4) Angstrom and beta = 96.53(3)degrees. The structure was solved from diffractometer data by a combination of direct and Fourier methods and refined by full-matrix least squares fit on the basis of 4846 observed reflections to R-1 and wR(2) values of 0.0224 and 0.0574, respectively. (C) 1998 Elsevier Science S.A. All rights reserved.