Entrapment of tert-Butyllithium and Lithium tert-Butylamide Monomers by Partially lithiated Deriatives of Aluminum and Gallium Primary Amide Complexes

摘要

The lithiation of the dimeric trisamido group 13 derivatives {M[N(H)t-Bu]3}2 (la, M = Al; Ib, M = Ga) by alkyllithium reagents RLi (R = t-Bu or Me), at different stoichiometries, was investigated. On the basis ofNMR data, the initiallithiation of la occurs at the bridging N(H)t-Bu groups to give the mono- and dilithiated derivatives Lix[Al2(Nt-Bu)x(NHt-Bu)6-x] (x = 1, 2). The reaction of la with t-BuLi in a 1:3 molar ratio in n-pentane at 23 °C produces {Li[Al(Nt-Bu)(NHt-Bu)ili2o(t-BuLi) (2) in 67% yield, whereas the treatment of la with MeLi in diethyl ether at 23 °C yields {Li[Al(Nt-Bu)(NHt-Bu)ili2.[LiN(H)t-Bu] (7) and {Li[Al(Nt- B1.KNH.t-R1.),!.l'!. (8). The gallium analogue of 7, i.e., {Li(Ga(Nt-Bu)(NHt-Bu)J}2.[LiN(H)t- ~u" ~), ~~'a.<:.ticl~ of lb with t-RuLi in a 1..3 molar ratio in n-pentane at 23 °C. The structures of 2, 5, and 7 have been determined by X-ray crystallography and were shown to involve the entrapment of a monomeric t-BuLi or LiN- (H)t-Bu fragment by a dilithiated derivative of la or Ib. The six fused four-membered rings give rise to a concave, lounge-chair arrangement for the 12-atom [LisA12N6E (E = Cor N)] clusters of2, 5, and 7. Variable-temperature lH NMR spectra of2, 5, and 7 in C7D8 over the range -90 to 23 °C reveal a fluxional process involving Li-N bond breaking and formation。